feat(rxNotify): check the stack exists before clearing it
feat(rxNotify): Adding test for non existent stack clear
feat(rxNotify): Added more checks to test and separated it on its own
fix(rxNotify): fix test to check for "to.not.throw(Error"
Merge pull request #369 from rackerlabs/rx-notify-stack-clear-fix

feat(rxNotify): Check the stack exists before clearing it