Change title and message property modifiers to copy
Fix presentation issue when using init directly

Though initWithTitle:message:delegate:cancelButtonTitle:otherButtonTitles: is the most commonly used initializer, there’s no reason init should not work. However, auto-layout balked when using just init because of the autoresizing masks. Common initialization functionality is now put in init, which is called by initWithTitle:message:delegate:cancelButtonTitle:otherButtonTitles:.
Add attributedTitle and attributedMessage properties