Add LateX support

[kinoute]

nbviewer.js started to implement LateX support : kokes/nbviewer.js@1c0d733

I updated this repo with their master branch in hope you could release a new version of nbviewer-app on brew supporting LateX.

Cheers

[kinoute]

nbviewer.js doesn't support all types of LateX (it ignores ones with "bad" syntax) but at least it's a start.

Without (0.1.3):

With this PR:

[tuxu]

Thanks a lot for the PR @kinoute. I just merged the latest master of nbviewer.js.

To keep track of the state of nbviewer.js, I'm using Git's subtree command

git subtree merge --squash --prefix=nbviewer.js/ nbviewer/master

where nbviewer is a Git remote pointing to the other repo. For this reason, I didn't merge your changes directly.