Updated to use authorized_response approach
Merge pull request #221 from mdxs/upd_authorized

Updated to use authorized_response approach
Handle case in which email is None (as GitHub can provide)
Merge pull request #222 from mdxs/fix_create_user_db

Handle case in which email is None (as GitHub can provide)
Added  rel="nofollow" to order and filter links
Used Flask-RESTful for API.
Fix fields type.
Improved API errors handler.
Added request.query_string value to JSON link.
Added 'check_unique_email' field to config API.
Sorted properties in CONFIG_FIELDS.
Added recaptcha fields.
Minor fix.
Sorted User fields.