Let "rightMenu" switch correctly when slideOutThenIn = YES.

issue:  slideOutThenIn = YES, "rightMenu" switch wrong.

In SASlideMenuContentSegue,

run       [destination performSegueWithIdentifier:@"rightMenu" sender:rootController];
before  switchToContentViewController animate slideOut , completed.
cause  SASlideMenuRightMenuSegue.perform [source.parentViewController == nil]

workaroud:
run    [destination performSegueWithIdentifier:@"rightMenu" sender:rootController];
after  (void) switchToContentViewController:(UINavigationController*) content completion:(void (^)(void))completion;




MARK:  My first github pull request.....