Rotation support

Rotation support: Headless fragments
Detail Fragment: Provides a detailed view of a specific entry
Currently ```MainActivity``` is where the user searches for feeds (but we might add new functionality later). Because of this, I thing ```FeedActivity``` would not make a great name (As the activity might do different things)

What's now ```FeedActivity```, show the entries for a specific feed, in fact the title of this actiivity will be the title of the Feed being shown. Hence, the name. But ```EntriesActivity``` would work just fine too. Let's further discuss this later