[TEST] Clean up db before Release#destroyAndCleanUp() test
[REFACTOR] Make Artist::allToJSON() use Ember namespace by default
[TEST] Artist::allToJSON()
[FEATURE] Release: add ::createMultiple() method
[TEST] Release::createMultiple()
[FEATURE] Artist: add ::createMultiple() method
[TEST] Artist::createMultiple()
[TEST] Artist#destroyAndCleanUp()
[TEST] Artist#setReleasesUsingIds()
[REFACTOR] Make Artist#toJSON() create Ember compatible json by default
[TEST] Artist#toJSON()
[TEST] Release: fix bugs in test and left over 'only'