`colors` package update would improve webpack compatibility

I'm trying to include this module in a project with webpack, which tries to gather up code into discrete bundles. It can't do this if it can't figure out where a `require` is likely to lead.

Older versions of `colors` included a `setTheme` method that took an arbitrary string and then tried to `require` that string directly, i.e. literally anything could possibly be required from literally anywhere... so webpack is in a bind. This was [resolved several years ago](https://github.com/Marak/colors.js/pull/203) in `colors`, and hopefully that dependency could be updated in the next release of `cli-table`.

I would have already opened a pull request myself today, but `colors` doesn't keep a changelog and I'm not sure how it's being used in this package, so I'm afraid of breaking something.