Merge pull request #2628 from teddyzeenny/testing-exceptions

Ember testing capture exceptions thrown in promises
Fix undefined error when promise rejected on startup

Router#targetHandlerInfos is not initialized when a
promise is rejected on startup, causing error
in Router#isActive
Merge pull request #2656 from machty/rejected-promise-app-load-fail

Fix undefined error when promise rejected on startup
Create Test Adapter to keep ember-testing framework agnostic