[BUGFIX beta] Fixed broken import of `generateController`
[BUGFIX beta] Add global API tests.

This just adds the basic layout/structure to add tests to confirm we
have no further regeressions.
Merge pull request #5134 from rjackson/add-global-api-tests

Export generateController and add regression test.
Fix Global's API test.

When using strict mode, this is not always defined properly. This just
uses `window`.
[DOC] Update CONTRIBUTING.md for commit prefixes and feature flags
Merge pull request #5137 from amiel/contributing-updates

[DOC] Update CONTRIBUTING.md for commit prefixes and feature flags
[FEATURE ember-metal-is-present]

Add Ember.isPresent as inverse of Ember.isBlank