Use numpy distutils to build irbempy

[jtniehof]

We're building the irbempy extension "by hand" with explicit calls to build irbem and then explicit f2py calls. @asreimer in #108 suggested using the numpy distutils for the build, with the extension class. Suggested example at https://github.com/aburrell/apexpy/blob/master/setup.py

I think I've looked at this in the past and it didn't play terribly well with some other stuff we were doing, but that was a long time ago and it's worth another look. We were also considering getting away from numpy distutils since it's been the cause of some problems (#45, 9da472340d23d0892ab0b828861372f8dcb3b908). It's also fixed some problems (3fcb9fdfe15834d7b27d90731f14bdd8dfccce65).

[jtniehof]

If we work on a new build system, there are probably other options to consider, e.g. https://mesonbuild.com/

EDIT: don't need to switch build systems necessarily, can also look at what they did for detecting this sort of thing.

[balarsen]

Doesn't #296 make this unneeded for IRBEM?

[jtniehof]

Even with #296 we still need IRBEM for L*, etc. (stuf that's in irbempy but not Coordinates).

[jtniehof]

Since I'm throwing general build system notes in here, thread on projects that can't build into wheels. We should be good with this given that, uh, we can build and install from wheels :) but in case something weird shows up there might be hints in there.

[jtniehof]

numpy distutils is no more, so this will not happen.