Minor cleanups of mixer.py
Drop 'settings', never used
Drop 'initial', never used - also a helper function that now is never called
And drop order_tracks, also not needed now
Drop max_play_time, never set or even looked at!
Drop samplerate - never set externally, hard-coded into member, and member never used!
Drop transition_time parameter and just set it in __init__
Reduce the oqueues to a forced one queue, and simplify corresponding code
Merge pull request #35 from Rosuav/mixercleanup

Mixercleanup