Use Utils.unescape_uri for user/password in Authorization header
Use Utils.unescape_uri for user/password in Authorization header

Should fix https://github.com/excon/excon/issues/604 which I hit
while trying to replicate a `curl` authenticated request whose
credentials include `+`. An identical `excon` request was generating
`401`s, and started to work after applying this change.

I haven't found a test associated to the way this header is encoded,
so I've only verified the change with the comparison mentioned above.

excon/excon