SoxBindings doesn't release GIL.

[pseeth]

Following discussion in #4, SoxBindings "works" in multithreading in that it doesn't fail, but it doesn't let you actually use multi-threading. We can fix that by releasing the GIL in the C extension.

[faroit]

@pseeth is there some news on this?

[lminer]

Is there any reason we can't use multiprocessing instead? The GIL isn't so much of an issue in that case. Or does it introduce too much overhead?