Merge pull request #36 from cbess/patch-1

Fix potential keyboard observer crash by cbess

Author: nicolaschengdev

WYPopoverController/WYPopoverController.m

@@ -2188,6 +2188,8 @@ - (void)keyboardWillHide:(NSNotification *)notification
 
 - (void)dealloc
 {
+    [[NSNotificationCenter defaultCenter] removeObserver:self];
+    
     barButtonItem = nil;
     passthroughViews = nil;
     viewController = nil;