Rename Marionette dependency to match docs

In all the examples I've seen, people use "marionette" as the dependency name. Marionette now has an AMD build which uses this name. See: https://github.com/marionettejs/backbone.marionette/wiki/Using-marionette-with-requirejs
Merge pull request #4 from stevewillard/patch-1

Rename Marionette dependency to match docs