Get Torii ready for use as an ember-addon

 * add ember-addon/index.js to provide include hooks
 * remove unused s3.js task options
 * update package.json to include 'ember-addon' keyword
 * update package.json to look good for npm publish
 * remove ember-shim and qunit-shim in vendor
 * clean up some unused directories in test/
 * update npmignore

Builds on excellent starting work done by @rondale-sc

cc @mixonic @rjackson

I think this looks good. I'm going to review it tomorrow and then publish to npm soon. I've tested using it locally (via `npm link`) and seems to work well. Torii has a module (`torii/ember`) that sets things up in the container, and I'm not sure how to do that automatically via the hooks provided by ember-addon yet, so there is still an additional setup step that users of torii and ember-cli will need to do, for the moment.