use Destructuring for require module

Currently, just Node.js **v6** enable `destructuring` by default. 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

Example:

From:

``` js
const isIP = require('net'). isIP;
const getType = require('mime-types').contentType;
```

To: 

``` js
const { isIP } = require('net');
const { contentType: getType } = require('mime-types');
```
