Depend on RBIntegrations 0.5b1
Depend on RBIntegrations 0.5b1

We are now depending on the `rbintegrations` package for third party
integrations.

Testing Done:
`setup.py develop` worked with `rbintegrations` pre-installed.

Reviewed at https://reviews.reviewboard.org/r/8854/

reviewboard/reviewboard,reviewboard/reviewboard,reviewboard/reviewboard,brennie/reviewboard,brennie/reviewboard,chipx86/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,brennie/reviewboard,chipx86/reviewboard,brennie/reviewboard