Fix Referer header to point to the original host name

[simov]

I have no idea how this has gone unnoticed for so long. Here is how our single test regarding that behavior looks like before and after the change using request-debug:

should have the referer when following redirect by default

{ request: 
   { debugId: 1,
     uri: 'http://localhost:6767/temp',
     method: 'POST',
     headers: 
      { cookie: 'foo=bar',
        host: 'localhost:6767',
        'content-length': 0 } } }
{ redirect: 
   { debugId: 1,
     statusCode: 301,
     headers: 
      { location: 'http://localhost:6767/temp_landing',
        'set-cookie': [Object],
        date: 'Fri, 23 Oct 2015 08:38:55 GMT',
        connection: 'close',
        'transfer-encoding': 'chunked' },
     uri: 'http://localhost:6767/temp_landing' } }
{ request: 
   { debugId: 1,
     uri: 'http://localhost:6767/temp_landing',
     method: 'GET',
     headers: 
      { cookie: 'foo=bar; ham=eggs',
-        referer: 'http://localhost:6767/temp_landing',
+        referer: 'http://localhost:6767/temp',
        host: 'localhost:6767' } } }
{ response: 
   { debugId: 1,
     headers: 
      { 'x-response': 'GET temp_landing',
        date: 'Fri, 23 Oct 2015 08:38:55 GMT',
        connection: 'close',
        'transfer-encoding': 'chunked' },
     statusCode: 200,
     body: 'GET temp_landing' } }

Referer header should point to the host name of the original resource when redirecting.

Hopefully that's the correct behavior.