Implementing __floordiv__ as shortcut for `.descendant`

[youtux]

Hi, I think it would be quite handy to have Expression.__floordiv__ being a shortcut for Expression.descendant.
The reasoning is that it is quite common to traverse nodes using the descendant selector in pure XPath (which is //), while calling .descendant makes the code quite verbose.

IMO it would be quite convenient to be able to type

x.current('table')//'tbody'//'tr'//'td'

instead of

x.current('table').descendant('tbody').descendant('tr').descendant('td')

What do you think?