fix didTap (it was using index function call instead of the index)

It looks like didTap was not not using the correct index here:

- (void)didTap:(UITapGestureRecognizer *)tapGesture
{
   if (!_delegate || [_delegate carousel:self shouldSelectItemAtIndex:index])


index here is actually a function: char	*index(const char *, int) __POSIX_C_DEPRECATED(200112L);