0.3.1: mostly bug fixes

This release fixes some small (or severe, depending on your point of view) problems:

• Big-endian platforms were broken, oops!
• It wasn't possible to mix int16 and float32 input data, not that you would really want to do that.
• Various tests didn't actually work
• It turns out -remove_noise was actually useful, so it has been brought back from the dead.