Add DOUAudioVisualizer.
DOUAudioVisualizer: use lroundf
DOUAudioVisualizer: rename _barGeometries to _bar
DOUAudioStreamer: add setHintWithAudioFile:
update example to use the streamer hint
DOUAudioFileProvider: bugfix for hint provider
update example project
DOUAudioFileProvider: remove __weak
update example to add audio visualizer
DOUEAGLView: make transparent and non-opaque