docs(toh-6/dart): quickfix to "BAD FILENAME" errors (#1929)

Exclude the new Observables section entirely for now.

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

@@ -89,6 +89,9 @@ block heroes-comp-add
 block review
   //- Not showing animated gif due to differences between TS and Dart implementations.
 
+block observables-section
+  //- TBC
+
 block filetree
   .filetree
     .file angular2_tour_of_heroes

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

@@ -359,7 +359,8 @@ block review
   figure.image-display
     img(src='/resources/images/devguide/toh/toh-http.anim.gif' alt="Heroes List Editting w/ HTTP")
 
-:marked
+block observables-section
+  :marked
     ## Observables
 
     Each `Http` method  returns an `Observable` of HTTP `Response` objects.
@@ -394,9 +395,9 @@ block review
 
     We start by creating `HeroSearchService` that sends search queries to our server's web api.
 
-+makeExample('toh-6/ts/app/hero-search.service.ts', null, 'app/hero-search.service.ts')(format=".")
+  +makeExample('toh-6/ts/app/hero-search.service.ts', null, 'app/hero-search.service.ts')(format=".")
 
-:marked
+  :marked
     The `http.get` call in `HeroSearchService` is similar to the `http.get` call in the `HeroService`.
     The notable difference: we no longer call `toPromise`. 
     We simply return the *observable* instead.
@@ -405,8 +406,8 @@ block review
     Let's create a new `HeroSearchComponent` that calls this new `HeroSearchService`. 
 
     The component template is simple - just a textbox and a list of matching search results.
-+makeExample('toh-6/ts/app/hero-search.component.html', null,'hero-search.component.html')
+  +makeExample('toh-6/ts/app/hero-search.component.html', null,'hero-search.component.html')
-:marked
+  :marked
     As the user types in the search box, a *keyup* event binding calls the component's `search` with the new search box value.
 
     The `*ngFor` repeats *hero* objects from the component's `heroes` property. No surprise there.
@@ -416,11 +417,11 @@ block review
     The `AsyncPipe` subscribes to the observable and produces the array of heroes to `*ngFor`.
 
     Time to create the `HeroSearchComponent` class and metadata.
-+makeExample('toh-6/ts/app/hero-search.component.ts', null,'hero-search.component.ts')
+  +makeExample('toh-6/ts/app/hero-search.component.ts', null,'hero-search.component.ts')
-:marked
+  :marked
     Focus on the `searchSubject`.
-+makeExample('toh-6/ts/app/hero-search.component.ts', 'searchSubject')(format=".")
+  +makeExample('toh-6/ts/app/hero-search.component.ts', 'searchSubject')(format=".")
-:marked
+  :marked
     A `Subject` is a producer of an _observable_ event stream. 
     This `searchSubject` produces an `Observable` of strings, the filter criteria for the name search.
 
@@ -430,8 +431,8 @@ block review
     We're going to access that `Observable` and turn the stream
     of strings into a stream of `Hero[]` arrays, the `heroes` property.
 
-+makeExample('toh-6/ts/app/hero-search.component.ts', 'search')(format=".")
+  +makeExample('toh-6/ts/app/hero-search.component.ts', 'search')(format=".")
-:marked
+  :marked
     If we passed every user keystroke directly to the `HeroSearchService`, we'd unleash a storm of http requests.
     Bad idea. We don't want to tax our server resources and burn through our cellular network data plan.
 
@@ -449,7 +450,7 @@ block review
     * `switchMap` calls our search service for each search term that makes it through the `debounce` and `distinctUntilChanged` gauntlet.
     It cancels and discards previous search observables, returning only the latest search service observable.
 
-.l-sub-section
+  .l-sub-section
     :marked
       The [switchMap operator](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/flatmaplatest.md)
       (formerly known as "flatMapLatest") is very clever.
@@ -468,7 +469,7 @@ block review
       Note that _canceling_ the `HeroSearchService` observable won't actually abort a pending http request
       until the service supports that feature, a topic for another day.
       We are content for now to discard unwanted results.
-:marked
+  :marked
     * `catch` intercepts a failed observable. 
     Our simple example prints the error to the console; a real life application should do better.
     Then it re-throws the failed observable so that downstream processes know it failed.
@@ -481,24 +482,24 @@ block review
     We could extend `Observable` with just the operators we need here by
     including the pertinent `import` statements at the top of this file.
 
-.l-sub-section
+  .l-sub-section
     :marked
       Many authorities say we should do just that.
-:marked
+  :marked
     We take a different approach in this example. 
     We combine all of the RxJS `Observable` extensions that _our entire app_ requires into a single RxJS imports file.
 
-+makeExample('toh-6/ts/app/rxjs-extensions.ts', null, 'app/rxjs-extensions.ts')(format=".")
+  +makeExample('toh-6/ts/app/rxjs-extensions.ts', null, 'app/rxjs-extensions.ts')(format=".")
-:marked
+  :marked
     We load them all at once by importing `rxjs-extensions` in `AppComponent`.
 
-+makeExample('toh-6/ts/app/app.component.ts', 'rxjs-extensions', 'app/app/app.component.ts')(format=".")  
+  +makeExample('toh-6/ts/app/app.component.ts', 'rxjs-extensions', 'app/app/app.component.ts')(format=".")  
-:marked
+  :marked
     Finally, we add the `HeroSearchComponent` to the bottom of the `DashboardComponent`.
     Run the app again, go to the *Dashboard*, and enter some text in the search box below the hero tiles.
     At some point it might look like this.
 
-figure.image-display
+  figure.image-display
     img(src='/resources/images/devguide/toh/toh-hero-search.png' alt="Hero Search Component")
 
 .l-main-section
@@ -554,7 +555,7 @@ block filetree
   - We extended HeroService to support post, put and delete calls.
   - We updated our components to allow adding, editing and deleting of heroes.
   - We configured an in-memory web API.
-  - We learned how to use Observables.
+  <li if-docs="ts"> We learned how to use Observables.</li>
   
   Below is a summary of the files we changed and added.