Extinction

Note: All releases since v0.4.0 have been for build system modernization of one sort or another.

Build system updates

- This release includes wheels uploaded to PyPI

Bugfixes

- Addressed `numpy.float` type deprecation warning introduced in numpy v1.20.

- Make `Fitzpatrick99` fully agree with IDL FM_UNRED (and original paper) by using natural boundary condition in cubic spline
- Speed up Fitzpatrick99() initialization from about 500us to 1us
- Speed up Fitzpatrick99 evaluation from about 50us to 6us (10 points)
- Add keyword argument for `r_v` to `fitzpatrick99` function so that `extinction.fitzpatrick99(wave, a_v, r_v)` works. This is consistent with calling conventions for `ccm89`, `odonnell94`, etc.