Fixed argument exchange

TypeError: undefined is not a function
    at Request._callback (/Users/kevireilly/Development/tests/node_modules/node-vine/lib/vine.js:49:11)
    at Request.self.callback (/Users/kevireilly/Development/tests/node_modules/node-vine/node_modules/request/request.js:122:22)
    at Request.EventEmitter.emit (events.js:98:17)
    at Request.<anonymous> (/Users/kevireilly/Development/tests/node_modules/node-vine/node_modules/request/request.js:888:14)
    at Request.EventEmitter.emit (events.js:117:20)
    at IncomingMessage.<anonymous> (/Users/kevireilly/Development/tests/node_modules/node-vine/node_modules/request/request.js:839:12)
    at IncomingMessage.EventEmitter.emit (events.js:117:20)
    at _stream_readable.js:919:16
    at process._tickCallback (node.js:419:13)