Add tests for Application#injectTestHelpers.

Adds tests to ensure that the `onInjectHelpers` callbacks are ran, and
ensures that the tests are run in a consistent state (prior to the
`cleanup` changes here we would leak `ajaxStart` and `ajaxStop` event
handlers).
Merge pull request #3576 from rjackson/add_tests_for_on_inject_helpers

Add tests for Application#injectTestHelpers.
fix invalid decumentation for using Ember.compute.empty with arrays
Merge pull request #3579 from stefanpenner/fix-empty-cp-docs

fix invalid decumentation for using Ember.compute.empty with arrays
[fixes #3072] Ember.run.later now behaves closer to setTimeout +
Ember.run
Ensure Ember.run.laters executeAt date is correclty coerced.
Added a test for test helper 'wait' to check for pending timers

Signed-off-by: hajee <hajee@moretIA.com>
Merge pull request #3582 from hajee/master

Added a test for test helper 'wait' to check for pending timers
Improve error message when action bubbles
Document available features.

Add `FEATURES.md` as a place for contributors to indicate what each
feature flag does and where we can find out more information about it.
Merge pull request #3583 from alexspeller/improve-action-error-message

Improve error message when action bubbles
Merge pull request #3584 from rjackson/make_features_listing

Document available features.
debounce and throttle accept string numbers like time interval
Merge pull request #3588 from marcioj/update-backburner

debounce and throttle accept string numbers like time interval
Updates `ember-dev` to (b0b12c4).

Updates `ember-dev` to (b0b12c4) which includes the following changes:

* Will not attempt to `unshallow` a full git repo
* Makes default test suite (packages only) run with features enabled and
  disabled.
* Fixes bug where the wrong Project name is used in the auto-generated
  CHANGELOG.
* Allows overriding the build type. (Simply set `ENV['BUILD_TYPE']='canary'`)
* Add `ember:generate_static_test_site` task to create a static HTML
  file for running the test suite.
* Add custom test results gathering for use in cross-browser testing.
* Make sure that the test file being used in the `Assetfile` is prefixed
  with the proper dasherized project name (prior to this Ember Data
  tests were still named `ember-tests.js` and now they will be
  `ember-data-tests.js`).
* Fixes issue where local `rake test` runs would attempt to perform git
  operations (`checkout` and `cherry-pick`). Now git operations will
  only be attempted if `ENV['CI']=true`.

For further reference:

https://github.com/emberjs/ember-dev/compare/0c0743979a...b0b12c4758e26
Generate static site tests.

This will publish a ember-tests.html static test site along with the
builds. This makes it extremely simple to test the latest
canary/beta/release builds on various devices. It is also critical to
the cross-browser testing that we have been working on.

This depends on changes in #3591.
Merge pull request #3592 from rjackson/static_test_generator

Generate static site tests.
Merge pull request #3591 from rjackson/update_ember-dev

Updates `ember-dev` to (b0b12c4).
Fix component name in documentation example
Merge pull request #3593 from denisnazarov/patch-2

Fix component name in documentation example