no sender sent to button action

[wtholliday]

If the QBPopupMenuItem was the sender, a single action could handle multiple menu items. This is good when the menu items are generated programatically.

For example:

- (void)contextMenuItemSelected:(id)sender {
  QBPopupMenuItem *item = (QBPopupMenuItem*) sender;
  assert(item); // This currently fails.
  [self performCommandNamed: item.title];
}

This change is as simple as modifying -[QBPopupMenuItemView performAction]:

[self.item.target performSelector:self.item.action withObject:self.item afterDelay:0];