docs(directives): ensure that the back-to-top directive resets location

Closes #6512
Closes #6499

Author: petebacondarwin

docs/app/src/directives.js

@@ -10,9 +10,10 @@ angular.module('directives', [])
  *
  * @description Ensure that the browser scrolls when the anchor is clicked
  */
-.directive('backToTop', ['$anchorScroll', function($anchorScroll) {
+.directive('backToTop', ['$anchorScroll', '$location', function($anchorScroll, $location) {
   return function link(scope, element) {
     element.on('click', function(event) {
+      $location.hash('');
       scope.$apply($anchorScroll);
     });
   };

docs/config/templates/indexPage.template.html

@@ -226,7 +226,7 @@ <h4 class="search-results-group-heading">{{ key }}</h4>
 
     <footer class="footer">
       <div class="container">
-        <p class="pull-right"><a back-to-top href="#">Back to top</a></p>
+        <p class="pull-right"><a back-to-top>Back to top</a></p>
 
         <p>
           Super-powered by Google  ©2010-2014