Adding UIWebView auto initialization of buggyfill.

UIWebView has the same issues as mobile safari when using viewport
units. This change makes the regex that matches Mobile Safari more
generic to match what UIWebViews report in iOS. Tested on iOS Simulator
UIWebView, iOS Simulator Mobile Safari, iOS 7 Mobile Safari, and iOS Twitter
Client UIWebView.

UIWebView
"Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X)
AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D167"

Mobile Safari
"Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X)
AppleWebKit/537.51.2 (KHTML, like Gecko) Version/7.0 Mobile/11D167
Safari/9537.53"