seekto 0 then stop playing.

stop will now behave the same when avplayer is used to play from a
stream as when avaudioplayer is used to play from a local file.

Fix for CB-57
Updated to use avplayer when url starts with http:// or https:// for
full streaming support.

All other urls will use the standard AVAudioplayer

Fix for CB-8222
Background thread on play to prevent locking during initial load of
media.

rate is enabled, otherwise media has to be stopped and started to change rate. Fixed error getting command args

github close #33

This reverts commit ca449e3b.