Add Decoder#canSeek, setPosition and getPosition. Implement those for VorbisDecoder.
Add Decoder#readSamples(float[])
Add CircularBuffer#skip and #getAvailable, modify combine for signed short.
Add CircularFloatBuffer
Merge pull request #261 from xoppa/audio

Audio: Add Decoder#canSeek, setPosition, getPosition, readSamples, CircularFloatBuffer, etc.