TBAutoHeightTextView

带有占位符，随着字符串长度自动增高的TextView（可用于对话框输入）

用法

    TBTextView *textView = [[TBTextView alloc] init];
    textView.frame = CGRectMake(20, 50, 100, 30);
    textView.backgroundColor = [UIColor colorWithWhite:0.9 alpha:1.0];
    [self.view addSubview:textView];