rather than a sound being emitted from a static starting position,
it is now emitted from a source object. This object may change
position, and the sound will follow him (updating the panning node's
position, velocity, and orientation accordingly).

Usage: new audio.PositionAudio({url:'./hi.ogg', sourceObject:player,
etc...})

the sourceObject may be any object that has position and velocity
attributes.

Note: I'm not convinced that orientation is correct, but I
don't think it's any more broken than it was before.
Rather than a sound being emitted from a static starting position,
it is emitted from a source object. This object may change
position, and the sound will follow him (updating the panning node's
position, velocity, and orientation accordingly).

Usage: new audio.PositionAudio({url:'./hi.ogg', sourceObject:player,
etc...})

the sourceObject may be any object that has position and velocity
attributes.

Note: Orientation of the source object is
being set. TODO: fix this