How to run any npm command

Hey @mattdesl,

This is by-far one of the best NPM runners I've tested, and I've tested ALOT. The console log output is great and it runs fast.

I'm using it to install modules using `install` but I also need to use the `run` and `publish` commands.

Doesn't seem that your exporting those.

I'd need something like this

```
module.exports.cmd = function(command) {
return command.bind(null, command)
}
```

Then I could use `npmCmd('run build')`. Thoughts on adding this and publishing an updated patch?

The issue names no file or test; start by reading the package's public API and how the existing install command is exposed. Determine the intended interface for run and publish, then verify that those commands are exported and that the updated package can be published.

Written by the indexing model from the issue text.