``pyuploadcare.dj.forms.FileField`` always returns URL
``pyuploadcare.dj.forms.ImageField`` always returns URL
``pyuploadcare.dj.forms.FileGroupField`` always returns URL
``pyuploadcare.dj.forms.ImageGroupField`` always returns URL
Merge pull request #61 from uploadcare/form-field-always-returns-url

Form field always returns url