RC1.3.1
- Forced vertical screen orientation
- Fixed bug: the current folder is listed in the top textview
- Replaced app and secret dropbox api keys

TODO:
  * Fix bugs: Icon of ebooks is not shown properly when the list is
ordered by date (if device VERSIOn < JELLY_BEAN)
  * Optimize performance
  
See Readme for more info about bugs and new improvements. A lot to do!

Signed-off-by: Sergio Carrasco (moncayo) <scarrascoh@gmail.com>