docs(lifecycle-hooks): update directive selector to camelCase

closes #1236

public/docs/_examples/lifecycle-hooks/ts/app/spy.component.ts

@@ -16,7 +16,7 @@ import {Spy} from './spy.directive';
       <button (click)="reset()">Reset Heroes</button>
     </p>` +
 // #docregion template
-    `<div *ngFor="let hero of heroes"  my-spy  class="heroes">
+    `<div *ngFor="let hero of heroes"  mySpy  class="heroes">
        {{hero}}
      </div>`
 // #enddocregion template

public/docs/_examples/lifecycle-hooks/ts/app/spy.directive.ts

@@ -6,8 +6,8 @@ let nextId = 1;
 
 // #docregion spy-directive
 // Spy on any element to which it is applied.
-// Usage: <div my-spy>...</div>
-@Directive({selector: '[my-spy]'})
+// Usage: <div mySpy>...</div>
+@Directive({selector: '[mySpy]'})
 export class Spy implements OnInit, OnDestroy {
 
   constructor(private _logger:LoggerService) { }