Check for textView equality in UITextViewDelegate methods in JSQMessagesViewController

[virl]

Because JSQMessagesViewController can be subclassed, I think we need to check for textView equality in following methods' implementations:

- (void)textViewDidBeginEditing:(UITextView *)textView
- (void)textViewDidChange:(UITextView *)textView
- (void)textViewDidEndEditing:(UITextView *)textView

So when subclassed vc overrides them and implements additional UITextFields, it can just call super.