Update verifier to support headers, parameters, and bodies

[piofusco]

Current, verifier only takes method and uri. It would be great if it could also support HTTP headers, URL parameters, and/or JSON bodies. Something like this

subject.verify(
    Method.GET, 
    "/greeting", 
    ["Some header": "some value"],
    ["parameter1":"value1"], // or something like this
    [:]
)