Use 'install_requires' instead of 'requires' in setup.py

[dukebody]

I've noticed that sphinx is not installed automatically when the package is installed via pip. Actually it doesn't either when doing python setup.py develop.

I believe this is because the wrong keyword requires is being used in setup.py, when it should be install_requires: http://setuptools.readthedocs.io/en/latest/setuptools.html?highlight=setup#new-and-changed-setup-keywords I've read that setuptools monkeypatches distutils, so even if in that file the setup function comes from distutils, install_requires should work.

Changing the keyword effectively triggers installation of sphinx when installing numpydoc. PR will come shortly.

[rgommers]

fixed in gh-56