Update the Update Checker xibs to Xcode 5
Create README.md
Merge pull request #6 from elia/master

Create README.md
Merge branch 'master' into lionAndLater

Conflicts:
	Update Checker Sources/SUStatus.xib
	Update Checker Sources/en.lproj/SUUpdateAlert.xib
Use libc++ on Lion and later.
Fiddling with the update xibs.
Better looking and manageable preference xib constraints.
Moving the preference pane to ARC.
Replace some deprecated Objective C method calls in the Preference Pane.