Grant and ReverseProxy using an extra path element
I have much success combining google and FB oauth into a single node script over ReverseProxy!  😁 
However, when I attempt to insert another "pathname" into the proxy, the callback fails.  in other words, when I am using `https://domain.com/GRANT/` everything appears to work just fine in the proxy, both google and FB allow me to successfully log in.   

But in the callback, I get back this:
 `The requested URL /oauth/connect/google/callback was not found on this server.`  
Somehow the `/GRANT/` pathname is getting lost, both on FB and Google, since it should be "/GRANT/connect/google/callback".  is there a config setting I am missing?  I have tried using the "path" element as well, but when I try setting that, I am no longer able to even access either FB or google, i get back "404 page not found"

```
    "oauth": {
        "redirect" : "/",
         "defaults" : {
                "protocol" : "https",
                "host" : "featherstest.website/feathers",
                "path" : "/feathers"    /* this seems to cause more problems for me */
        },
      "facebook": {
        "key": "5XXXXXXXXXXXXXXXX4",
        "secret": "7XXXXXXXXXXXX8a",
        "scope": ["public_profile, email"]
      },
      "google": {
        "key": "81XXXXXXXXXXXXXdi.apps.googleusercontent.com",
        "secret": "XI2XXXXXXXXXXXXXXXMi",
        "scope": [
          "email",
          "profile",
          "openid"
        ]
      }
    }
```
any suggestions?