Prevent race condition in node.visible?

Sometimes Capybara would get stuck trying to find a node which has actually disappeared, because node.visible? was trying to wait for that node to reappear.
tagged 1.1.4
Allow protocol relative URLs, backported from #776
Merge pull request #907 from mscottford/topic/backport-protocol-relative-fix

Allow protocol relative URLs, backported from #776