Change Carrierwave storage from GridFS to Roz.

Also migrates the files over.

***NOTICE***
You should run rake db:migrate locally. Remotely it should run as part
of deployment. Ensure Roz settings are correct before migrating.
Set Roz URLs for staging and production
Merge pull request #9 from biola/gridfs_to_roz

Change Carrierwave storage from GridFS to Roz.