Support $ref links.

[ben-gibson]

It would be really useful if JSON Schema references where linked.

{
    "properties": {
        "foo": {
            "type": "object",
            "allOf": [
                {
                    "$ref": "#/definitions/bar"
                }
            ]
        }
    },
    "definitions": {
        "bar": {
            "type": "object",
            "properties": {
                
            }
        }
    }
}