add logout router

router/logout.js

+//登出
+module.exports = (req, res, createWebAPIRequest, request) => {
+  const cookie = req.get('Cookie') ? req.get('Cookie') : ''
+  createWebAPIRequest(
+    'music.163.com',
+    '/weapi/logout',
+    'POST',
+    {},
+    cookie,
+    (music_req, cookie) => {
+      res.append("Set-Cookie", cookie)
+      res.send(music_req)
+    },
+    err => res.status(502).send('fetch error')
+  )
+}