Remove region add duplicate event

fixes #1839
Typo in changelog

and --> on
Updates API README
Fix spelling
Update region-manager.jsdoc
Fix typo
Revert "Throw a descriptive error for collectionViews"

This reverts commit 1df40a88f3e34a10cfabd07135669099cbac94bc.
Bump and build v2.2.1
Update upgrade guide to follow semver
Update marionette.functions.md

added item about proxy unbindEntityEvents - 'Marionette.proxyUnbindEntityEvents'
Update marionette.itemview.md

The old example for 'variable' in the documentation did not work for me. The 'settings' argument is the 2nd or 3rd argument of the _.template function. The model is then passed in as a parameter to the then generated template function. I attempted to update the documentation to reflect this.
Improve comments in region.show. Small cleanups.
Update marionette.object.md

updated 'Basic Use' item
Fix broken logo path
Adds helper methods to AppRouter.
region._ensureViewIsIntact

Having the region check for view.isDestroyed does two things:

1. It allows you to handle the error of a region.show without the region killing the currentView and breaking without recourse.

2. appending isDestroyed to a Backbone.View on region empty adds the same safety for not re-showing a removed backbone view.

The extra return this; was removed to prevent jslint error for too many statements, and seemed unnecessary
Improves Application triggerMethod arguments.
Update param types for addRegion method
Removes unnecessary emptyRegions call in LayoutView.
Updates file names; remove unnecessary files.