Added a homepage link to getbootstrap.com

makes sense, no?
Currently, there is no link in the Expo to the main Bootstrap website.

_layouts/default.html

@@ -12,7 +12,7 @@
           <script type="text/javascript" src="http://platform.twitter.com/widgets.js"></script>
         </div>
         <h1><a href="http://expo.getbootstrap.com">Bootstrap Expo</a></h1>
-        <span class="tagline">Beautiful and inspiring uses of Bootstrap</span>
+        <span class="tagline">Beautiful and inspiring uses of <a href="http://www.getbootstrap.com">Bootstrap</a></span>
       </div>
     </div>