Added build watch for e2e tests

As a follow up from #323 I've added build watch, I'm looking for you comments @bparees @ironcladlou 
we may want to stress test (and unit test for that matter) them, but e2e test probably isn't the place to do it.

As for which way we go here in particular, i'm pretty indifferent.  I do prefer the simplicity of the poll loop, but it is also nice to have an example of how to use watches so i'd be ok w/ merging this if only for that reason.  I don't think either path is worth losing a lot of sleep over.