country directory not installed using npm package

When using the node package with `npm install -g coronavirus-tracker-cli`, the country directory is not installed. This results in the following error: 

```javascript
internal/modules/cjs/loader.js:628
    throw err;
    ^
Error: Cannot find module '../lib/country/us'
...
```
This is not an issue if using `cd <source_dir> && npm install -g`. 