Removes IIFE patterns in source.

Ain't nothin' wrong with an IIFE, but by removing them our Object definitions become slightly more consistent across the codebase. Which is a big :+1: to me.

This gets rid of the IIFE around RegionManager per @paulovieira's suggestion. While I was at it, I also got rid of the one around `triggerMethod` (with the added bonus of removing an unnecessary argument passed to it).

Behaviors is the last one with an IIFE...but that code is basically a mess. It's a big enough refactor to merit its own PR.
Should `RegionManager` extend `Marionette.Object` instead of `Controller`? Is that breaking?