cython dependency.

[rzu512]

When I try to install crick by pip3, pip3 doesn't install Cython automatically.

$ pip3 install crick --user

Collecting crick
  Using cached crick-0.0.3.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-y1mcfhjt/crick/setup.py", line 7, in <module>
        from Cython.Build import cythonize
    ModuleNotFoundError: No module named 'Cython'
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-y1mcfhjt/crick/

[jcrist]

This is a bit tricky to do cleanly due to how setup.py scripts are run. I'll resolve this for sure before the next release, but the resolution might be just to remove cython completely (see #17).

Note that binary releases are available for all OS's with conda, and for osx (currently) on pypi. A manylinux and windows build setup could be done for pypi as well, but it's not high priority for me.

[shughes-uk]

@jcrist poke

[MuellerSeb]

This is solved with the pyproject.toml that defines build time dependencies.

Added here: #39

[milesgranger]

Thanks, @MuellerSeb!