Elminate UITextAlignment deprecation warnings.

Use NSTextAlignment on iOS 6 and UITextAlignment on iOS 5. Solution based
on examples from http://stackoverflow.com/q/11920321/79202.
Merge pull request #42 from theory/alignment-deprecation

Elminate UITextAlignment deprecation warnings.
Update README.md
introduced an -insets value for every style able image
Removed ImageButton from Storyboard to keep aesthetic consistency 
Consolidated background-image-insets support into +[NUISettings getImage:withClass:]
Refactored categories to expose an applyNUI method
Used applyNUI instead of NUIRenderer on UINavigationBar's bar button items to fully apply NUI
Merge branch 'master' of https://github.com/savage7/nui