Update ember-test-helpers
Update ember-test-helpers

This wil remove the deprecation warnings. Fixes https://github.com/switchfly/ember-mocha/issues/42
cowboyd/ember-mocha,Robdel12/ember-mocha,alexgb/ember-mocha,alexgb/ember-mocha,switchfly/ember-mocha,jeffreybiles/ember-mocha,Robdel12/ember-mocha,alexgb/ember-mocha,SaladFork/ember-mocha,emberjs/ember-mocha,switchfly/ember-mocha,cowboyd/ember-mocha,Robdel12/ember-mocha,SaladFork/ember-mocha,cowboyd/ember-mocha,switchfly/ember-mocha,emberjs/ember-mocha,jeffreybiles/ember-mocha,SaladFork/ember-mocha,jeffreybiles/ember-mocha