fixed find() bug

find() was calling selector_to_xpath() in the loop, breaking the selector after the second call.

I have included 2 tests in t/find.t. The first one tests the fixed bug described above.
The second test is:

      is wq('<html>1</html>')->find('html')->size, 1, 'find() includes root elements';

This test fails. I dont know if its a bug or a feature, could you elaborate on that?

Thank you.