added basic validations and specs
changed create_with_omniauth method to create_from_hash which is a simpler method
created methods to find authorization from oauth hash and to create a new authorization based on the same hash
rewrote omniauth callback controller to use new methods from authorization
Merge pull request #457 from diogob/refacto_user

Refacto user
fixing project video iframe url
Merge branch 'master' of github.com:catarse/catarse