removed loopUntil associated key, it was unneeded since loop until is only used within a single method, added waitForStatus:timeout:withBlock

waitForStatus:timeout:withBlock

works better in scenarios where the notify: method is fired asynchronously even before waitForStatus has a chance to start, where status would be updated but self.notified gets trampled and set back to NO when waitForStatus: starts.  This ensures that self.notified and expected status are set prior to running the test step that will eventually call notify:
added test cases for the waitForStatus:timeout:withBlock:
removed commented out loopUntil associated object key
Merge pull request #6 from Simulacrotron/master

Added block based waitForStatus:timeout: method