Added fragments.
Remade the model to avoid exposing internal classes.
Added adapters for model classes.
Added menu options to article fragment
Added functionality to menu buttons
Updated fragment listeners and made MainActivity implement them
Changed article open action to avoid ShareActionProvider.
Fixed threading issue on startup (AsyncTask callback in doInBackground)
Added null check to article open action.
Added 'swipe to refresh' functionality to article list.
Removed unused code.