 Test failed:  'util' is assigned a value but never used

Running tests using `npm test` command fails with this error:

```
> node-alias@0.2.12 test /workspaces/node-alias
> standard && mocha

standard: Use JavaScript Standard Style (http://standardjs.com)
  /workspaces/node-alias/lib/encode.js:2:5: 'util' is assigned a value but never used.
npm ERR! Test failed.  See above for more details.
```