Refactor Backbone Notifications

Models are extraneous for something as temporary as a notifaction -- this change
moves all the configuration into the views, and removes the models entirely.

cms/static/coffee/src/main.coffee

@@ -18,11 +18,11 @@ $ ->
   $(document).ajaxError (event, jqXHR, ajaxSettings, thrownError) ->
     if ajaxSettings.notifyOnError is false
       return
-    msg = new CMS.Models.ErrorMessage(
+    msg = new CMS.Views.Notification.Error(
         "title": gettext("Studio's having trouble saving your work")
         "message": jqXHR.responseText || gettext("This may be happening because of an error with our server or your internet connection. Try refreshing the page or making sure you are online.")
     )
-    new CMS.Views.Notification({model: msg})
+    msg.show()
 
   window.onTouchBasedDevice = ->
     navigator.userAgent.match /iPhone|iPod|iPad/i