docs(tutorial/7 - Routing

On line 173, added alt attribute for WCAG 1.1.1

docs/content/tutorial/step_07.ngdoc

@@ -170,7 +170,7 @@ __`app/partials/phone-list.html`:__
 
       <ul class="phones">
         <li ng-repeat="phone in phones | filter:query | orderBy:orderProp" class="thumbnail">
-          <a href="#/phones/{{phone.id}}" class="thumb"><img ng-src="{{phone.imageUrl}}"></a>
+          <a href="#/phones/{{phone.id}}" class="thumb"><img ng-src="{{phone.imageUrl}}" alt="{{phone.alt}}></a>
           <a href="#/phones/{{phone.id}}">{{phone.name}}</a>
           <p>{{phone.snippet}}</p>
         </li>