Add pianobar module

Pianobar is a console-based player for pandora.com. This module will show the current playing song and add mouse events for next song, play/pause and volume management. It is important to ensure to set fifo and event_cmd options on pianobar config file.
For the event_cmd use https://github.com/jlucchese/pianobar/blob/master/contrib/pianobar-song-i3.sh