Add superagent and supertest definitions

supertest/supertest-tests.ts

@@ -0,0 +1,16 @@
+/// <reference path="supertest.d.ts" />
+/// <reference path="../express/express.d.ts" />
+
+import supertest = require('supertest')
+import express = require('express');
+
+var app = express();
+
+supertest(app)
+  .get('/user')
+  .expect('Content-Type', /json/)
+  .expect('Content-Length', '20')
+  .expect(201)
+  .end((err, res) => {
+    if (err) throw err;
+  });