Only return null on error in FriendsNetworkTask

Make sure to return null only if there was an error, this makes it
easier to handle the result in the callback function (same like in
Anime-/MangaNetworkTask).
Add missing letter to description in AboutActivity

In app_description was a "u" missing in "beautifully".
Update Picasso and Retrofit

Added new versions of the Picasso and Retrofit libraries.
Update ABS and SND

Updated to the latest SherlockNavigationDrawer and ActionBarSherlock.

Potentially, fixes #62 as there is a note in the ABS changelog about an
issue with OEM resources being fixed.
Merge pull request #96 from d-sko/descfix

Add missing letter to description in AboutActivity
Merge pull request #95 from d-sko/friendlistfix

Fix wrong error crouton on friendlist
Merge remote-tracking branch 'upstream/working' into working