[beta] Use documentElement instead of body for ember-extension detection
[FEATURE string-parameterize] Revert feature.

During the weekly core team meetings this feature has been determined to
be a better fit for an external plugin.
[FEATURE ember-testing-simple-setup] Revert feature.

During the weekly core team meetings it was decided that while the
intentions were good, this feature is really just covering up the real
issue but not addresing the underlying problem.
Merge pull request #4418 from teddyzeenny/document-element

Use documentElement instead of body for ember-extension detection
Merge pull request #4452 from rjackson/revert-string-parameterize

[FEATURE string-parameterize] Revert feature.
Merge pull request #4453 from rjackson/revert-ember-testing-simple-setup

[FEATURE ember-testing-simple-setup] Revert feature.
Update CHANGELOG for 1.5.0-beta.3.
[BUGFIX beta] Allow components with layoutName specified by parent class to specify templateName