Attempt to pass doc through a pager

Follow-up from #548.

When using `man`, the output was paged. You could achieve the same effect by running this:

```
wp help core config --color | less -r
```

I suspect there's some issue with the escape sequence generated by php-cli-tools, since when I run that, the output skips the "NAME" header. Omitting the `--color` flag has no effect.