_.includeIn store the includedMixins and _.extend the extendedMixins
test includedMixins and extendedMixins
bump version (0.3.1)
_.includeIn use included mixin property for trigger  a callback after each include;
_.extendIn use extended mixin property for trigger a callback after each extend;
tests for extended and included callbacks
bump version (0.3.2)