Made it possible to force serialization to skip all fields that are None.

This is useful because many API's (like AWS) expect keys to be missing
when you want to use the default value. See the added test for example usage.
Bumped the version
Merge pull request #5 from plain-vanilla-games/model_wide_serialize_when_none

Made it possible to force serialization to skip all fields that are None
Merge remote-tracking branch 'jokull/master' into jokull

* jokull/master:
  Bumped the version
  Made it possible to force serialization to skip all fields that are None.

Conflicts:
	tests/test_serialize.py
Skip removed fields from primitive data when applying role
Merge branch 'fix-roles-with-model-wide-serialize-when-none' into jokull

* fix-roles-with-model-wide-serialize-when-none:
  Skip removed fields from primitive data when applying role