[FEATURE ember-testing-simple-setup]

Removes the need for most of the ceremony of setting up an application for testing. The following
examples are equivalent:

Ember 1.0.0 type testing setup:

```javascript
App = Ember.Application.create();
App.setupForTesting();
App.injectTestHelpers();
```

New simple setup:

```javascript
App = Ember.Application.create({testing: true});
```
Merge pull request #3785 from rjackson/enable_simpler_testing_setup

[FEATURE ember-testing-simple-setup]