Let "rightMenu" switch correctly when slideOutThenIn = YES.

issue:  slideOutThenIn = YES, "rightMenu" switch wrong.

In SASlideMenuContentSegue,

run  [destination performSegueWithIdentifier:@"rightMenu"
sender:rootController];
before switchToContentViewController animate completed.

workaroud:
run  [destination performSegueWithIdentifier:@"rightMenu"
sender:rootController];
after switchToContentViewController.(completed)

SASlideMenuRightMenuSegue.perform [source.parentViewController == nil]
修改Demo工程