Update dev dependency

To test for mem leaks, just run node test/runner.js
and follow the instructions.

package.json

@@ -24,7 +24,7 @@
     "http-proxy": "~0.10"
   },
   "devDependencies": {
-      "node-webkit-agent": "~0.1.2"
+      "webkit-devtools-agent": "~0.2.1"
   },
   "engines": {
     "node": ">=0.6.6",

test/runner.js

@@ -38,7 +38,7 @@ setupRedirectServer(function() {
  *  if the devtools agent is available, omitted otherwise.
  */
 function setupCORSServer(callback) {
-    var child = fork('./sub-server', [host, port]);
+    var child = fork('./sub-server', [host, port], {cwd: __dirname});
     child.on('message', function(message) {
         if (message.hasDevtoolsAgent) {
             callback(function() {
@@ -56,7 +56,7 @@ function setupCORSServer(callback) {
 }
 
 function setupRedirectServer(callback) {
-    var child = fork('./sub-no-cors-server', [host, portServer]);
+    var child = fork('./sub-no-cors-server', [host, portServer], {cwd: __dirname});
     child.once('message', function() {
         callback();
     });