User#refresh_feed no longer returns the list of entries. It will raise a NotSubscribedError if it is passed a feed to which the user is not subscribed.

This means application logic must change; when requesting a feed refresh, after receiving the "OK" response the client will have to request its entries, the same as if the user clicked on a feed to read its entries. This simplifies pagination: pagination logic can be onl associated with entries retrieval, not with feed refreshing.
FeedsController#update no longer returns the updated list of entries, just a status header. The angularjs service, after receiving an OK response to the refresh request, issues a GET request to retrieve the list of entries via FeedsController#show.

This simplifies design: we only have to worry about pagination in FeedsController#show (well and in FoldersController#show, but that's not yet implemented).