Refactor globals into a separate module.
Remove skate.destroy() and skate.unregister() methods. They're not inline with the current web component specifications and were only really intended for testing. Since we have access to the modules internally, we can use that for cleaning up in tests.
Merge pull request #95 from skatejs/GH-92

Use global registry and document observer.
Merge branch 'master' of github.com:skatejs/skatejs into release-task