Moved ``get_bucket_name`` from forms to StorageMixin.
Added ``get_file`` method to ``ValidateS3UploadForm``, which returns the open file from storage.
Added docstrings to ValidateS3UploadForm.
Changed ``get_file`` method to ``get_file_path`` on ``ValidateS3UploadForm``.
Corrected typo bug in settings, which was not returning SET_CONTENT_TYPE correctly.
Merge branch 'development'