added a 'listen' option

Webframe now listens by default even if you pass in your own server.

README.md

 Options:
 
 * `server`: Your own HTTP (like the one created by http.createHttpServer).
+* `listen`: Whether to call the `listen` method on the server. Defaults to
+  true.
 * `port`: The port to listen on. Defaults to the PORT environment variable, or
   8080.
 * `host`: The host to listen on. Defaults to the HOSTNAME environment variable,

index.js

 			this.server = options.server;
 		} else {
 			this.server = http.createServer();
+		}
 
+		// Listen
+		if (options.listen !== false) {
 			var port = options.port || process.env.PORT || 8080;
 			var host = options.host || process.env.HOSTNAME || "127.0.0.1";
 

package.json

 {
   "name": "webframe",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "description": "Web framework.",
   "main": "index.js",
   "scripts": {