allow passing an agent through to node http requests, closes #68

lib/adapters/http.js

@@ -52,7 +52,8 @@ module.exports = function httpAdapter(resolve, reject, config) {
     port: parsed.port,
     path: buildUrl(parsed.path, config.params).replace(/^\?/, ''),
     method: config.method,
-    headers: headers
+    headers: headers,
+    agent: config.agent
   };
 
   // Create the request