Refactor to use ember-test-helpers

The core logic in ember-qunit has been extracted to switchfly/ember-test-helpers.

This library now wraps ember-test-helpers with qunit-specific helpers.
Merge pull request #99 from dgeb/separate-test-helpers

Refactor to use the extracted lib ember-test-helpers
Add a few more npm scripts.

* Add `npm run build` to generate the build.
* Add a `prepublish` script to ensure that bower packages are installed
  on `npm install` (but not from consumers).
* Add `npm start` to run `broccoli serve`.
Merge pull request #100 from rwjblue/add-more-scripts

Add a few more npm scripts.
Fix Travis badge URL.
Make a plain named-amd build.

Prep for publishing by creating a single AMD build file that does not
contain the loader, tests, etc.
Add JSHint to build.
Merge pull request #102 from rwjblue/make-plain-amd-build

Build process updates.