fix bootstrap modal use for "add content"

Author: Andy Olliver

app/views/cms/application/_add_content_modal.html.erb

@@ -1,3 +1,3 @@
-<div id="modal-add-content" class="modal fade modal-content" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
-
+<div id="modal-add-content" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
+ <div class="modal-content"></div>
 </div>