Test scripts and Travis integration

These changes add a top-level test script and set things up for automatic continuous integration via Travis CI.  You can just run `python scripts/install.py` to install dependencies, and then `npm test` to run the five test scripts.  Note that the Travis build is currently failing:

https://travis-ci.org/msridhar/jalangi/builds/13657241

Maybe this is an Ubuntu issue, as all tests pass locally on my Mac.