Change in the AngularJS controller name, to make it more sensible.
Hide buttons in the navbar while bootstraping angularjs and in pages without angularjs enabled.
Use angularjs to display buttons in the navbar only when a feed is currently selected for reading.
Instead of disabling the "add subscription" button while a newly added feed is being loaded, hide it.

Adding a "disabled" class to a link actually does nothing; it does not look different if it's part of a Bootstrap navbar, and it does not prevent the method pointed by ng-click from being invoked.
Moving a feed to a folder (existing or new) or removing a feed from its folder no longer returns a JSON response but just an HTTP success or error code.

It's not necessary that the server sends back any more information than a success/failure indicator. Since adopting angularjs the web client has enough information to update the view.
Adapted the "remove feed from its folder" functionality to angularjs.
Use angularjs directives for the folders dropdown menu, instead of composing it as a rails partial.

This makes it easy to add/remove folders from the dropdown, simply by adding/deleting them from the scope.
Adapt the "move feed to an already existing folder" functionality to angularjs.
Removed alert that appeared when user tried to move a feed to the folder it's already at.

This alert was supposed to appear when the server responds with an HTTP 304 when moving a feed to a folder, but this never actually happens anymore. If the server is requested to move a feed from a folder to the same folder, nothing actually happens at the database level but the server responds happily with an HTTP 200. Therefore all the code related to showing an alert when a 304 is received can be safely removed.

This is actually desirable. It makes no sense to tell the user an error has happened simply because he's clicked on an already checked folder in the dropdown. It's better to silently do nothing.