Upgrade path

I've been working on updating this repository with several updates:

1. update dependencies including ember-test-helpers and ember-source
2. add ability to pass down options to setupContext
3. Add a rudimentary UI to the test page

These are all updates I've made in my fork, specifically the ember-mocha-compat branch https://github.com/yads/ember-mocha/tree/ember-mocha-compat

The first 2 features are handled by #633, once these are merged I can submit another PR for the UI test page.