Change `test-support` folder for `addon-test-support` (#234)

* Change `test-support` folder for `addon-test-support`

This is a new ember addon thing. Supported since Ember-CLI 2.1.

TODO: Update static site guides with new infomation & migration guide

* Update paths in tests

* Update migration guide

* v4.0.0-beta.2

Test Deploy

Released v3.1.1

Released v3.1.0

Released v3.0.1

Released v3.0.0

Released v2.2.3

Released v2.2.2

Released v2.2.1