Borderlands 2 Audio plugin

Hi,

I don't know if this is the right way to do this, but here's an updated version of the Borderlands 2 Positional audio plugin. This one work well with the 1.5.0, the current version on Steam. Also included are informations on how to update it for future versions, in case I don't do it.

 - Update for Borderlands 2 version 1.5.0
 - Fixed invalid version checking
 - Added details on how to peek the vectors for future references