Add RACCommand support to UIAlertView
Improve docs for UIAlertView.rac_command.
Clean up UIAlertView+RACCommandSupport.

Also adds a warning if the delegate is non-nil when hijacking.
Document that UIAlertView.rac_command overrides the delegate
Unset alert view delegate when unsetting command.
Improve docs for UIAlertView+RACCommandSupport.
Unset the associated object when unsetting the delegate
Merge remote-tracking branch 'origin/2.0-development' into hh-uialertview-raccommandsupport

Conflicts:
	ReactiveCocoaFramework/ReactiveCocoa.xcodeproj/project.pbxproj
Rewrite UIAlertView support to use delegate proxy
Update alert view tests to match implementation
Fix alert view test description
Change AlertView signal to use rac_description
Merge pull request #591 from henrikhodne/hh-uialertview-raccommandsupport

Add RACSignal support to UIAlertView