Merge pull request #38 from pinda/master

Added selected state for UIButton
Added Button background-image-selected and font-color-selected to README
Made miscellaneous README updates
Added a note about copying NUIStyle.nss, other README updates
Added support for UISwitch. Not yet fully-working due to infinite loop issue
further changes to switch implementation
Finished initial support for UISwitch
Cleaned up naming and placement of some UISwitch code
Added initial autoupdate support
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.
Add assert to ensure a file exists.

Took me a while to track down that I had a typo in my file name, because the
exception thrown was from NSRegularExpression. So add an `NSAssert()` to save
other future developers from themselves.
Removed deprecated render:onDrawRect:withClass from NUINavigationBarRenderer
Made NUISettings setAutoUpdatePath return void
Improved support for background-* changes during autoupdate
Updated podspec to 0.2.3
Added autoupdate directions to the README
Merge branch 'autoupdate'
Added support for more background and border properties to BarButton
Added +[NUIGraphics backButtonWithClass:]
Made insets larger for BarButtons