Preserve encoded values in proxied URLs.

When proxying requests to URLs that contain encoded URLs, the requests contained
URL is decoded because Go stores a URL's Path field in decoded form. As a result,
any encoded values in a URL are lost.

Fixes #65
One more comment - I would set expected URL in the outer scope, otherwise the in case of request failure the test would pass, as you are not checking the request success result and the actualURL would then match expectedURL as they would be both empty strings.