docs(cleanup): fix bad h3 markup and normalize headings

Closes #5341

modules/angular2/src/router/instruction.ts

@@ -46,7 +46,7 @@ export class RouteParams {
  *
  * You can inject `RouteData` into the constructor of a component to use it.
  *
- * ## Example
+ * ### Example
  *
  * ```
  * import {bootstrap, Component, View} from 'angular2/angular2';

modules/angular2/src/router/router.ts

@@ -129,7 +129,7 @@ export class Router {
   /**
    * Dynamically update the routing configuration and trigger a navigation.
    *
-   *##Usage
+   * ### Usage
    *
    * ```
    * router.config([
@@ -148,7 +148,7 @@ export class Router {
    * Navigate based on the provided Route Link DSL. It's preferred to navigate with this method
    * over `navigateByUrl`.
    *
-   *##Usage
+   * ### Usage
    *
    * This method takes an array representing the Route Link DSL:
    * ```