Add CI to pyret.org

[peblair]

In a similar vein to #4, there really should be some sort of repository-level configuration for pyret.org's deployment process. I would set up something myself and open a PR, but the deployment seems to be done manually on Brown's servers (which I have no way of accessing).

Pinging @jpolitz and @shriram, since I'd imagine they're the most likely to be able to address this.