Setup Travis CI build system.
Add in hopefully correct dependencies.
Add back xetex.
Build script now terminates on error.
Merge branch 'f/terminate-build-script' into upstream/build-system
The "script" field no longer does cd nonsense.
Add texlive-math-extra as a dependency
Add the cd stuff back in.

it turns out it wasn't pointless. it was needed because the build script assumes
you are in its directory.
Add texlive-latex3 as a dep
Merge branch 'build-system' into develop
Merge branch 'build-system' into develop
Merge branch 'develop' of github.com:learnmath/lysa into develop
Add travis image to the readme.

This will have a little icon saying if the build passed.
travis icon now goes above title in readme
get rid of line break between title and travis icon
Travis icon now goes after the title
Merge branch 'develop' of github.com:learnmath/lysa into develop
Have PDFs be deployed on every build.
Build status in the README now links to the site.
Update .travis.yml to publish a release if it's tagged.