chore(docs): rename @private to @internal

The latter is understood by TypeScript's --stripInternal option, so this lets us
rely more on the tooling provided by typescript team.

modules/angular2/src/router/instruction.ts

@@ -144,7 +144,7 @@ export class ComponentInstruction {
   reuse: boolean = false;
 
   /**
-   * @private
+   * @internal
    */
   constructor(public urlPath: string, public urlParams: string[],
               private _recognizer: PathRecognizer, public params: {[key: string]: any} = null) {}

modules/angular2/src/router/router_outlet.ts

@@ -32,7 +32,7 @@ export class RouterOutlet {
   private _currentInstruction: ComponentInstruction = null;
 
   /**
-   * @private
+   * @internal
    */
   constructor(private _elementRef: ElementRef, private _loader: DynamicComponentLoader,
               private _parentRouter: routerMod.Router, @Attribute('name') nameAttr: string) {