$ref property of path item object is not able to reference a file in the same domain. 

The below piece of code is in swagger.json

``` js
"paths":{
 "/path/to/action":{
 "$ref":"http://same.domain.com/action_doc.json"
 }
}
```

references another file in the same domain.
As shown in the example here
https://github.com/swagger-api/swagger-spec/blob/master/fixtures/v2.0/json/resources/resourceWithLinkedDefinitions.json#L32

Any advise would be helpful.
