Fixed callbacks
Merge pull request #326 from GrahamCampbell/2.1-callback

[2.1] Fixed Callbacks
Test improvements
Merge pull request #327 from GrahamCampbell/2.1-tests

[2.1] More Testing Improvements
Merge remote-tracking branch 'origin/2.1'
Merge remote-tracking branch 'origin/master' into experimental

Conflicts:
	tests/DefinitionTest.php
	tests/FactoryMuffinTest.php