Merging katex-fonts into the main KaTeX repo

[kevinbarabash]

Having the font generation code in the same repo would simplify the process for making font changes. One of the concerns in the past was that having the font files in the repo would bloat the repo. While this has been addressed in part by #54, I think we could take things even further by using Git LFS (Large File Support) for the binary font files.

https://git-lfs.github.com/