WIP: add support for native font load events.
Also spy on the native font watch runner when testing.
Use document.fonts to feature detect native font events so it works well with testing and loading in other frames.
Clean up native font watch runner constructor.
Fix toCssString method.
Prevent closure compiler from complaining about a new API returning a Promise.
Add spec for Font#toCssString.
Add new test fixtures for the native font API.
Fix reference to loadWindow.document and make sure the reject callback is not called with an error.
Add specs for the native font watch runner. These are not executed if the browser does not support native font events.
Do not use document.fonts.check to check if a font has loaded as it only includes fonts in the document and returns true if the font is unknown.
Clean up native font watch runner specs.
Add timeout to the native font loader.
Remove reference to Source Sans D in native font loader spec.
Update compiler and simplify native font watch runner code.
Merge pull request #184 from typekit/bs-native-fontloader

Add support for native font load events.