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.
```

Start by running `npm test` and inspect the reported assignment at `lib/encode.js:2`. Check the surrounding code to determine why the `util` value is present, then confirm the issue is resolved when the Standard check and Mocha tests both pass.

Written by the indexing model from the issue text.