serpy

• Don't catch AttributeError and KeyError for MethodField

• Revert behavior in #38, and match behavior in DRF which is:

| | required=True | required=False | | --- | --- | --- | | data = {'value': 1} | {'value': 1} | {'value': 1} | | data = {'value': None} | {'value': None} | {'value': None} | | data = {} | KeyError('value',) | {} |

• If required=False, None values will now be dropped from the output
• MethodFields with required=True will trigger an exception when None value is returned
• Drop support for Python 2.6
• Add support for Python 3.5 and 3.6

• Added label parameter to Field to be able to specify the output label
• Updated documentation

API changes:

• argument for the object to be serialized changed name from obj to instance
• Serializer now takes context kwarg and ignores it for Django REST Framework compat
• Serializer now takes data kwarg and errors for Django REST Framework compat