Preventing supports tests from being wrapped in ()

The shorthand method is called on all tests, this.supports as well as this.media. Only this.media testst should be wrapped in () by the shorthand method. Including an extra test for 'width' being present in the tested string prevents supports tests from begin wrapped into e.d. '(webp)', and thus causing false negatives.
Merge pull request #3 from micschk/develop

Preventing supports tests from being wrapped in ()