Add setup classifiers

[vatai]

@lmantill, apparently there are "project classifiers" (or classifications?) on pypi! You should check them out at this link and copy them here (use the nice big COPY button next to the desired category). If I understand correctly this helps organize pypi packages into a hierarchy of topics/classes.

What I thought was relevant:

Intended Audience :: Science/Research
Intended Audience :: Education
License :: OSI Approved :: MIT License
Natural Language :: English
Programming Language :: Python
Topic :: Documentation :: Sphinx
Topic :: Education
Topic :: Scientific/Engineering
Topic :: Scientific/Engineering :: Chemistry
Topic :: Scientific/Engineering :: Physics

[lmantill]

This is nice! I'll add some to your list.