Add unwrap to babysitter and wreqr to remove UMDs

Pulling some of the changes from #1290 into master to fix UMDs in 1.8.x. [See this thread](https://github.com/marionettejs/backbone.marionette/pull/1290#issuecomment-42443355)

**Changes:**
- Add unwrap to babysitter and wreqr
- Switch from concat build step to preprocessed one
- Add marionette.bundle build file