iOS 5.0 compatibility.

I have added the necessary checks/tests to ensure compatibility with iOS 5.0.

The tradeoff (for now) is that you cannot set the bold effect when auto completing, as UIKit started officially supporting NSAttributedString until iOS 6.0.

But everything else works :smile:

No loss of functionality can be achieved using CoreText, but this should be enough for now.

I tested it on iOS 5.1, but Deploymate has validated it should work all the way back to iOS 5.0.

Awesome component by the way!