Removed section about ARC support from README.
Removed section about ARC support from README.

There are now two officially supported ways to use MASShortcut: through
including the Xcode project in your app’s workspace and linking against
MASShortcut.framework, and through CocoaPods. Both options work well in both
ARC and MRC projects with no additional settings needed. (I use MASShortcut in
a MRC project myself.)

MacPaw/MASShortcut,shpakovski/MASShortcut,shpakovski/MASShortcut,baz/MASShortcut,ianyh/MASShortcut,mpapp/MASShortcut,shpakovski/MASShortcut,MacPaw/MASShortcut