Accelerating various ops

[bmcfee]

Just jotting this down before I forget.

librosa 0.5 will add dynamic time warping (not totally relevant for amen), and as a side-effect, optional numba jit compilation for certain methods.

This should make it much easier to accelerate certain bottleneck ops like zero-crossing alignment.

[tkell]

:emoji indicating optimization:

[tkell]

Hello @bmcfee, I hope your day is excellent! Amen is now running on librosa 0.7.0 - is the numba magic that you added there enough to do these speedups, or are there changes that need to be made in amen?

[bmcfee]

Not sure, i'll have to take a skim through the amen code to see.