Add ability to select multiple files for playing background tracks.
New button to go to next background track.
------- v2.9.0 (Apr 2015)
Fix problem with loading background WAV files.
Option to turn off input clipping detection.
------ v2.8 (Oct 2014)
New Vibrato effect
Send WAV files from Looper Pedal (Lo-Fi)
Prepare for Android 5.0 (Lollipop)