Ember Oauth2 Versions Save

• Update ember-cli
• Use ES6
• Update Tests
• cleanup

• ember-cli-babel as dependecy
• format with Prettier
• fix travis.ci build for headless google chrome

• fix typo in scope
• update ci to use Chrome headless
• update ci to use node 6.11

Converted to EmberAddon and turned EmberOAuth2 into a service

• Updated testing to use Ember-Qunit
• Update project README

• Update NPM author info

• add setProvider method
• change init to not take providerId

• Add verifyToken method to handle mitigation of the confused deputy
• Fix bug with checking of state

• Update getState function to not take a param argument and use the configure statePrefix to find the state from localStorage.
• This makes getState and getToken perform the same way and avoids confusion with the api
• fix bug where handleRedircect could not find the stateObj

• Drop support for deprecated callback methods onSuccess, onError, and onRedirect. Callbacks can be called using Ember.Evented trigger with the targets success, error, and redirect.

• Add support Authorization Grant Flow