Add pulse notifications for wiki revisions, forum posts, questions, and answers.

This is not meant to be merged at this time. This doesn't solve the problem of where the mozillapulse module lives (http://hg.mozilla.org/users/josh_joshmatthews.net/mozillapulse/), nor does it provide any error handling if publishing a message fails. This is designed to spur conversation about what kind of data to provide in the pulse messages, and clear up any further technical questions.