docs(toh-6): search query fixes

closes #2008
Changes:
- Drop `asObservable()` since it is deprecated in RxJS 5 (see the
[migration
guide](https://github.com/ReactiveX/RxJS/blob/master/MIGRATION.md#operat
ors-renamed-or-removed)).
- Drop `+` from hero search query URL: `app/heroes/?name=${term}+`. At
best it is interpreted as a regex op that serves no purpose, at worst,
it gets interpreted as a space (cf. [HTML 4.01 section
17.13.4](https://www.w3.org/TR/REC-html40/interact/forms.html#h-17.13.4)
).
- Rename `searchSubject` to `searchTerms`
- Other minor tweaks to prose.

This work is in preparation for #1924.

Note: toh-6 tests pass.

public/docs/_examples/toh-6/ts/app/dashboard.component.html

@@ -1,13 +1,10 @@
 <!-- #docregion -->
 <h3>Top Heroes</h3>
 <div class="grid grid-pad">
-<!-- #docregion click -->
   <div *ngFor="let hero of heroes" (click)="gotoDetail(hero)" class="col-1-4">
-<!-- #enddocregion click -->
     <div class="module hero">
       <h4>{{hero.name}}</h4>
     </div>
   </div>
 </div>
 <hero-search></hero-search>
-

public/docs/_examples/toh-6/ts/app/hero-search.component.ts

@@ -17,23 +17,22 @@ export class HeroSearchComponent implements OnInit {
   // #docregion search
   heroes: Observable<Hero[]>;
   // #enddocregion search
-  // #docregion searchSubject
+  // #docregion searchTerms
-  searchSubject = new Subject<string>();
+  searchTerms = new Subject<string>();
-  // #enddocregion searchSubject
+  // #enddocregion searchTerms
 
   constructor(
     private heroSearchService: HeroSearchService,
     private router: Router) {}
-  // #docregion searchSubject
+  // #docregion searchTerms
 
   // Push a search term into the observable stream.
-  search(term: string) { this.searchSubject.next(term); }
+  search(term: string) { this.searchTerms.next(term); }
-  // #enddocregion searchSubject
+  // #enddocregion searchTerms
   // #docregion search
 
   ngOnInit() {
-    this.heroes = this.searchSubject
+    this.heroes = this.searchTerms
-      .asObservable()           // cast as Observable
       .debounceTime(300)        // wait for 300ms pause in events
       .distinctUntilChanged()   // ignore if next search term is same as previous
       .switchMap(term => term   // switch to new observable each time
@@ -41,9 +40,8 @@ export class HeroSearchComponent implements OnInit {
         ? this.heroSearchService.search(term)
         // or the observable of empty heroes if no search term
         : Observable.of<Hero[]>([]))
-
       .catch(error => {
-        // Todo: real error handling
+        // TODO: real error handling
         console.log(error);
         return Observable.of<Hero[]>([]);
       });

public/docs/_examples/toh-6/ts/app/hero-search.service.ts

@@ -9,11 +9,9 @@ export class HeroSearchService {
 
   constructor(private http: Http) {}
 
-  // #docregion observable-search
   search(term: string) {
     return this.http
-               .get(`app/heroes/?name=${term}+`)
+               .get(`app/heroes/?name=${term}`)
                .map((r: Response) => r.json().data as Hero[]);
   }
-  // #enddocregion observable-search
 }

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

@@ -419,11 +419,11 @@ block observables-section
     Time to create the `HeroSearchComponent` class and metadata.
   +makeExample('toh-6/ts/app/hero-search.component.ts', null,'hero-search.component.ts')
   :marked
-    Focus on the `searchSubject`.
+    Focus on the `searchTerms`.
-  +makeExample('toh-6/ts/app/hero-search.component.ts', 'searchSubject')(format=".")
+  +makeExample('toh-6/ts/app/hero-search.component.ts', 'searchTerms')(format=".")
   :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.
+    This `searchTerms` produces an `Observable` of strings, the filter criteria for the name search.
 
     Each call to `search` puts a new string into this subject's _observable_ stream by calling `next`.
 
@@ -439,8 +439,6 @@ block observables-section
     Fortunately we can chain `Observable` operators to the string `Observable` that reduce the request flow.
     We'll make fewer calls to the `HeroSearchService` and still get timely results. Here's how:
 
-    * The `asObservable` operator casts the `Subject` as an `Observable` of filter strings.
-
     * `debounceTime(300)` waits until the flow of new string events pauses for 300 milliseconds 
     before passing along the latest string. We'll never make requests more frequently than 300ms.
 
@@ -495,11 +493,11 @@ block observables-section
   +makeExample('toh-6/ts/app/app.component.ts', 'rxjs-extensions', 'app/app.component.ts')(format=".")
 
   :marked
-    ### Adding the search component to the dashboard
+    ### Add the search component to the dashboard
 
-    We add the `HeroSearchComponent` to the bottom of the `DashboardComponent` template.
+    We add the hero search HTML element to the bottom of the `DashboardComponent` template.
 
-  +makeExample('toh-6/ts/app/dashboard.component.html', null, 'dashboard.component.html')
+  +makeExample('app/dashboard.component.html')
 
   :marked
     And finally, we import the `HeroSearchComponent` and add it to the `directives` array.