Element#to_s gave an <Element: Undefined> while Element#inspect gave a better output like <Element: [div id="some_div"]>
don't check for document but check if tagName exists
alias to_s to inspect as it does exactly the same
use outerHTML for to_s Element.to_s
Merge pull request #35 from roy/master

Let Element#to_s behave the same as Element#inspect