Wired up various Playback classes to watch System.hidden, and pause while in the background.

Signed-off-by: Kipp Ashford <kipp@seven2.net>
Remember if the Playback was already paused when hiding.

Signed-off-by: Kipp Ashford <kipp@seven2.net>
Fix to pause sounds when iOS device is locked or when Safari goes into the background.

Signed-off-by: Kipp Ashford <kipp@seven2.net>
Merge pull request #114 from volkipp/pause_sound_bg

Playback classes now wired to watch System.hidden, and pause while in the background