Updating backbone.marionette to 1.5.1 and backfill

Sources:
https://github.com/marionettejs/backbone.marionette/releases/*.zip -
files take from /lib/ directory of each archive.

Also fixes https://github.com/cdnjs/cdnjs/issues/1786 - 404 now
resolved. .map files merged where available.
Merge pull request #2564 from petecooper/master

Updating backbone.marionette to 1.5.1 and backfill