Fix name of vagrant box
Fix version number to major.minor.micro
initdb: Factor user creation code into a function
student.py: Create UPLOAD_FOLDER if does not exist
Update .gitignore
Clean-up configurations

 * vagrant/ contains a configuration to deploy and provision a vagrant
   VM where tigergrader is run as a WSGI apache application and celery
   is started a a daemon.

 * debug/ contains a configuration to quickly test or debug tigergrader.
   Everything is run on the local machine, the internal Flask debug
   server is used.