Subreddit search and ActionBar menu handling

-Subreddit search has been integrated into the drawer menu.
-ActionBar search button has been replaced with “search submissions”
(yet to be implemented)
-ActionBar menu changes on fragment interactions
-ActionBar search/Subreddit search hides keyboard upon losing focus (by
tapping outside or changing fragment)

TODO:
-Implement submissions search
-UI (colors/icons/etc)