* Remote spec for non-existent entry_classes helper method

This method no longer exists, and is handled by a local variable in a partial
instead.

* Remove spec for non-existent Account#ping! method

Removes:

- avatar_for_status_url
- relative_time
- reblogged_by_me_class
- favourited_by_me_class

* Remove unused helper files

* Add coverage for application helper

* Add coverage for StreamEntriesHelper #display_name