fix a parameter name issue, add a synchronous request call

let request = YYHRequest(url: NSURL(string: "http://www.google.com/"))
request.parameters["name"] = "value"

Microsoft IIS would've got a parameter name as "?name". This patch fixed it.
I need to take care of request response (not returned data) myself. I can't process the response in a synchronous request so I need to put a "&" reference mark in call as you can see, and this property observer would buy me a chance to do what I need.