Upgrade to Ember-CLI 2.11.1

[Gmfholley]

I upgraded the project to ember-cli 2.11.1 (also upgrades many of the other modules). I was unable to use this addon in our project without this update.

Ember tests pass and Ember server is running without warnings.
I also tested it with my own project and it seems to work well.

• baseURL was deprecated but converting to rootURL did not fix the tests. Adding <base href="/> to the test's index.html file allowed the tests to run properly.
  https://www.emberjs.com/blog/2016/04/28/baseURL.html
• moved the ember-cli-test-loader from bower to an npm module based on deprecation warnings
• updated the setup & teardown of tests to the new way