Avoid redirect from npmjs.org

```bash
$ curl --head npmjs.org
HTTP/1.1 301 Moved Permanently
Server: nginx/1.4.6 (Ubuntu)
Date: Sat, 11 Oct 2014 16:58:25 GMT
Content-Type: text/html
Content-Length: 193
Connection: close
Location: https://www.npmjs.org/
```