pink run fails with Error: Cannot find module 'ansi'

I'm using node v8.6.0 and npm v5.3.0 (installed via `nvm`, in case that matters). I was trying to get pink running so I could view https://github.com/bodil/are-we-there-yet locally. `npm install -g pink` worked, but `pink run` (or `pink` anything, it seems) fails with:

```
module.js:529
throw err;
^

Error: Cannot find module 'ansi'
at Function.Module._resolveFilename (module.js:527:15)
at Function.Module._load (module.js:476:23)
at Module.require (module.js:568:17)
at require (internal/module.js:11:18)
at Object. (/home/adamm/.nvm/versions/node/v8.6.0/lib/node_modules/pink/bin/pink.js:11:12)
at Module._compile (module.js:624:30)
at Object.Module._extensions..js (module.js:635:10)
at Module.load (module.js:545:32)
at tryModuleLoad (module.js:508:12)
at Function.Module._load (module.js:500:3)
```

Reproduce the failure with `npm install -g pink` followed by `pink run`, then inspect the referenced entry point at `/home/adamm/.nvm/versions/node/v8.6.0/lib/node_modules/pink/bin/pink.js`. Trace how the `ansi` module is expected to be available and verify that the `pink` command starts successfully after the fix.

Written by the indexing model from the issue text.