Adding sqs unit tests 4.1.x - Fixed circular reference errors reported by Travis when Taylor tried to merge the 4 month old PR

Rebased my adding_sqs_unit_tests_4.1.x branch to the 4.1 branch and changed the use of m::mock('DateTime') in testDelayedPushWithDateTimeProperlyPushesJobOntoSqs to use Carbon instead.  That fixed the circular reference errors being reported by Travis.