Adding support to multiple screens.

Nowadays, MM doesn't supports multiple screens (e.g. tablets) in a great way.
We starting to add this by replacing activities to fragments.

Some references:

Supporting Multiple Screens
http://developer.android.com/guide/practices/screens_support.html

Designing for Multiple Screens
http://developer.android.com/training/multiscreen/index.html

Fragments:
http://developer.android.com/guide/components/fragments.html
Migrated some activities to fragments

For now, we have migrated the main screen, the author list and
partially the playlist list.

This was made following this post blog:
http://suelengc.com.br/blog/?p=360
Added a default case on switch main menu
Now, the Playlist button main menu works.
Added some screenshots
Resolved the "ghost" fragment (Playlist) problem.

But the problem yet appears when we changed the device orientation
Merge pull request #3 from adorilson/fragmentation

Fragmentation