Handle relative URL parsing in IE.
Handle relative URL parsing in IE.

- Internet explorer does not set the protocol and host properties
  of an element when the URL is a relative URL -- so we have to
  fall back to using `window.location` in that case.

Spec-Ops/credentials-polyfill,digitalbazaar/credentials-polyfill,digitalbazaar/credentials-polyfill,Spec-Ops/credentials-polyfill