Added fragment for self.reddit submissions

-added Markdown parser library (Boost) to parse the selftext. library
compiled with ndk-build; placed inside the jniLibs directory.
-SelfSubmissionFragment displays both the contents and comments
together, but still needs some clean up + organization.
-action bar navigation mode list changed to action bar menu item.

TODO:
-handle activity and fragment lifecycle methods (app crashes often when
‘home’ button is pressed while viewing certain fragments).
-Optimize the display of submission content + comments list.