Complete AMD module extraction (tested with ember-cli)

So it turns out that my previous pull request works for AMD and commonJS modules, but doesn't work for ember-cli modules. :grimacing:

This pull request changes the way the factory-guy module is defined, and generates a file into dist/amd/factory-guy.js that returns the `FactoryGuy` variable as the default value. It's tested with ember-cli, and I'll be sending a pull request to ember-cli-data-factory-guy shortly to use the newest version of FactoryGuy.

Thanks!