Expose http.IncomingMessage and http.OutgoingMessage

lib/http.js

@@ -137,6 +137,7 @@ function IncomingMessage (connection) {
   this.client = this.connection;
 }
 process.inherits(IncomingMessage, process.EventEmitter);
+exports.IncomingMessage = IncomingMessage;
 
 IncomingMessage.prototype._parseQueryString = function () {
   var parts = this.uri.queryString.split('&');
@@ -192,6 +193,7 @@ function OutgoingMessage () {
   this.finished = false;
 }
 process.inherits(OutgoingMessage, process.EventEmitter);
+exports.OutgoingMessage = OutgoingMessage;
 
 OutgoingMessage.prototype.send = function (data, encoding) {
   var length = this.output.length;