Update fonts from MathJax

Summary:
Also, rename all of our uses of fonts to use the uppercased versions. We want to
use the uppercase versions because it makes updating and modifying the fonts
much easier (since the font names inside the actual font files are uppercased).

Test Plan:
  - Make sure the huxley screenshots look good (You can compare a diff of them
    on github at
    https://github.com/Khan/KaTeX/commit/f90d0933618da04ce2e5311fde026a7110d0c708
    By my eye, it seems like some things have moved up ~1/2 pixel, and some of
    the fonts have maybe slightly changed shape, like the large `b` in
    SizingBaseline)

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D11979