Use celery task to validate GTFS feeds on upload.

Add celery, Rabbit MQ, and Google's feedvalidator.py to project.
Run feedvalidator on uploaded GTFS in asynchronous celery task.
Cleanup in response to feedback
Resolve merge conflicts in provisioning file
Merge pull request #5 from flibbertigibbet/feature/celery-upload

Use celery task to validate GTFS feeds on upload.