Added ability to deploy to Google App Engine

Server functionality at least works locally. Deployment still needs to be
tested. Heroku deployment is likely broken now.
Refactor server to require modules only on GAE.

If the server isn't running on GAE the modules directory isn't added to the
python path, meaning all modules used are those installed in the environment
itself.
Merge branch 'master' of github.com:losttime/gdg-twilio