issue 621/async promise chunking

@gitnik @cthrax 

I chose bluebird as it is known to be faster, I also got tired of trying to make $q work on specs. All the rootscope.$apply()'s were having no effect on digest cycles. Maybe you guys can tell me where to correct it? Otherwise we gain an external dependency.

please review.

I also tried $digest and it did not work either [suggested here](http://stackoverflow.com/questions/21616766/angularjs-promise-callback-not-trigged-in-jasminejs-test)