docs(toh-6): copyedits (#3434)

- Remove statement that doesn't apply: "We recommend registering
app-wide services in the root
  `AppModule` *providers*" - but that isn't being done.
- Adding parentheses after method names; a few were missed in the
previous pass.
- `debounce()` --> `debounceTime()`
- Remove obsolete Dart prose.
- Fix heading indentation.
- Added missing closing `</span>`.
- Fix misnamed Jade variables.

cc @kapunahelewong

public/docs/ts/latest/tutorial/toh-pt6.jade

@@ -41,6 +41,7 @@ code-example(language="sh" class="code-shell").
     This command runs the TypeScript compiler in "watch mode", recompiling automatically when the code changes.
     The command simultaneously launches the app in a browser and refreshes the browser when the code changes.
 
+:marked
   You can keep building the Tour of Heroes without pausing to recompile or refresh the browser.
 
 .l-main-section#http-providers
@@ -54,7 +55,7 @@ block http-library
     You're ready to import from `@angular/http` because `systemjs.config` configured *SystemJS* to load that library when you need it.
 
 :marked
-  ### Register for HTTP services
+  ## Register for HTTP services
 
 block http-providers
   :marked
@@ -73,16 +74,9 @@ block http-providers
 :marked
   ## Simulate the web API
 
-  We recommend registering app-wide services in the root
-  `!{_AppModuleVsAppComp}` *providers*.  <span if-docs="dart">Here you're
-  registering in `main` for a special reason.</span>
-
   Until you have a web server that can handle requests for hero data,
   the HTTP client will fetch and save data from
   a mock service, the *in-memory web API*.
-  <span if-docs="dart"> The app itself doesn't need to know
-  about this, so you can slip the in-memory web API into the
-  configuration above the `AppComponent`.</span>
 
   Update <span ngio-ex>!{_appModuleTsVsMainTs}</span> with this version, which uses the mock service:
 
@@ -205,7 +199,7 @@ block get-heroes-details
 
 - var rejected_promise = _docsFor == 'dart' ? 'propagated exception' : 'rejected promise';
 :marked
-  In this demo service, you log the error to the console; in real life,
+  This demo service logs the error to the console; in real life,
   you would handle the error in code. For a demo, this works.
 
   The code also includes an error to
@@ -220,11 +214,11 @@ block get-heroes-details
   That's fine for a simulation, but it's wasteful to ask a real server for all heroes when you only want one.
   Most web APIs support a _get-by-id_ request in the form `api/hero/:id` (such as `api/hero/11`).
 
-  Update the `HeroService.getHero` method to make a _get-by-id_ request:
+  Update the `HeroService.getHero()` method to make a _get-by-id_ request:
 +makeExcerpt('src/app/hero.service.ts', 'getHero', 'src/app/hero.service.ts')
 
 :marked
-  This request is almost the same as `getHeroes`.
+  This request is almost the same as `getHeroes()`.
   The hero id in the URL identifies which hero the server should update.
 
   Also, the `data` in the response is a single hero object rather than !{_an} !{_array}.
@@ -255,21 +249,21 @@ block get-heroes-details
   ### Add the ability to save hero details
 
   At the end of the hero detail template, add a save button with a `click` event
-  binding that invokes a new component method named `save`.
+  binding that invokes a new component method named `save()`.
 
 +makeExcerpt('src/app/hero-detail.component.html', 'save')
 
 :marked
-  Add the following `save` method, which persists hero name changes using the hero service
+  Add the following `save()` method, which persists hero name changes using the hero service
-  `update` method and then navigates back to the previous view.
+  `update()` method and then navigates back to the previous view.
 
 +makeExcerpt('src/app/hero-detail.component.ts', 'save')
 
 :marked
-  ### Add a hero service _update_ method
+  ### Add a hero service _update()_ method
 
-  The overall structure of the `update` method is similar to that of
+  The overall structure of the `update()` method is similar to that of
-  `getHeroes`, but it uses an HTTP `put()` to persist server-side changes.
+  `getHeroes()`, but it uses an HTTP `put()` to persist server-side changes.
 
 
 +makeExcerpt('src/app/hero.service.ts', 'update')
@@ -305,7 +299,7 @@ block get-heroes-details
   When the given name is non-blank, the handler delegates creation of the
   named hero to the hero service, and then adds the new hero to the !{_array}.
 
-  Implement the `create` method in the `HeroService` class.
+  Implement the `create()` method in the `HeroService` class.
 +makeExcerpt('src/app/hero.service.ts', 'create')
 
 :marked
@@ -318,7 +312,7 @@ block get-heroes-details
   Each hero in the heroes view should have a delete button.
 
   Add the following button element to the heroes component HTML, after the hero
-  name in the repeated `<li>` tag.
+  name in the repeated `<li>` element.
 
 +makeExcerpt('src/app/heroes.component.html', 'delete', '')
 
@@ -344,12 +338,12 @@ block get-heroes-details
 
 :marked
   To place the delete button at the far right of the hero entry,
-  add this additional CSS:
+  add this CSS:
 
 +makeExcerpt('src/app/heroes.component.css', 'additions')
 
 :marked
-  ### Hero service `delete()` method
+  ### Hero service _delete()_ method
 
   Add the hero service's `delete()` method, which uses the `delete()` HTTP method to remove the hero from the server:
 
@@ -388,8 +382,8 @@ block observables-section-intro
   But requests aren't always done only once.
   You may start one request,
   cancel it, and make a different request before the server has responded to the first request.
-  A *request-cancel-new-request* sequence is difficult to implement with *!{Promise}s*, but
+  A *request-cancel-new-request* sequence is difficult to implement with *!{_Promise}s*, but
-  easy with *!{Observable}s*.
+  easy with *!{_Observable}s*.
 
   ### Add the ability to search by name
   You're going to add a *hero search* feature to the Tour of Heroes.
@@ -407,9 +401,8 @@ block observables-section-intro
   Instead you return the *Observable* from the the `htttp.get()`,
   after chaining it to another RxJS operator, <code>map()</code>,
   to extract heroes from the response data.
-
   RxJS operator chaining makes response processing easy and readable.
-  See the [discussion below about operators](#rxjs-imports).
+  See the [discussion below about operators](#rxjs-imports).</span>
 
 :marked
   ### HeroSearchComponent
@@ -439,7 +432,7 @@ block observables-section-intro
 :marked
   #### Search terms
 
-  Focus on the `!{_priv}searchTerms`:
+  Focus on `!{_priv}searchTerms`:
 
 +makeExcerpt('src/app/hero-search.component.ts', 'searchTerms', '')
 
@@ -471,8 +464,8 @@ block observable-transformers
 
     * `debounceTime(300)` waits until the flow of new string events pauses for 300 milliseconds
     before passing along the latest string. You'll never make requests more frequently than 300ms.
-    * `distinctUntilChanged` ensures that a request is sent only if the filter text changed.
+    * `distinctUntilChanged()` ensures that a request is sent only if the filter text changed.
-    * `switchMap()` calls the search service for each search term that makes it through `debounce` and `distinctUntilChanged`.
+    * `switchMap()` calls the search service for each search term that makes it through `debounceTime()` and `distinctUntilChanged()`.
     It cancels and discards previous search observables, returning only the latest search service observable.
 
   .l-sub-section