[fix] Empty Chat Messages

Disables the submit button on the Chat form, when no message is present.
Also, removed the `data-` prefix from the various Chat view elements.

modules/chat/client/views/chat.client.view.html

@@ -1,28 +1,28 @@
 <!-- The chat view -->
-<section class="container" data-ng-controller="ChatController">
+<section class="container" ng-controller="ChatController">
   <div class="page-header">
     <h1>Chat Example</h1>
   </div>
   <!-- The message form -->
   <form class="col-xs-12 col-md-offset-4 col-md-4" ng-submit="sendMessage();">
     <fieldset class="row">
       <div class="input-group">
-        <input type="text" id="messageText" name="messageText" class="form-control" data-ng-model="messageText" placeholder="Enter new message">
+        <input type="text" id="messageText" name="messageText" class="form-control" ng-model="messageText" placeholder="Enter new message">
         <span class="input-group-btn">
-          <button type="submit" class="btn btn-primary">Submit</button>
+          <button type="submit" class="btn btn-primary" ng-disabled="!messageText.length">Submit</button>
         </span>
       </div>
     </fieldset>
   </form>
   <ul class="list-unstyled">
     <!-- List all messages -->
-    <li class="col-xs-12 col-md-offset-4 col-md-4 chat-message" data-ng-repeat="message in messages">
-      <small class="pull-right text-muted" data-ng-bind="message.created | date:'mediumTime'"></small>
-      <img data-ng-src="{{message.profileImageURL}}" alt="{{message.username}}" class="pull-left chat-profile-image" />
+    <li class="col-xs-12 col-md-offset-4 col-md-4 chat-message" ng-repeat="message in messages">
+      <small class="pull-right text-muted" ng-bind="message.created | date:'mediumTime'"></small>
+      <img ng-src="{{message.profileImageURL}}" alt="{{message.username}}" class="pull-left chat-profile-image" />
       <div class="pull-left chat-message-details">
-        <strong data-ng-bind="message.username"></strong>
+        <strong ng-bind="message.username"></strong>
         <br>
-        <span data-ng-bind="message.text"></span>
+        <span ng-bind="message.text"></span>
       </div>
     </li>
   </ul>