Add tooltip to reload button

Closes #462

// FREEBIE

background.html

@@ -10,7 +10,7 @@
             <li><a class='show-debug-log'>{{ submitDebugLog }}</a></li>
         </ul>
       </div>
-      <span class='socket-status'></span>
+      <span class='socket-status' title='Restart Signal'></span>
       <div class='tool-bar clearfix'>
         <!-- <button class='show-new-conversation'></button> -->
         <input type='search' class='search' placeholder='{{ searchForPeopleOrGroups }}'>