Add chruby options

[opes]

Refactors and adds options for the chruby segment. Documentation updated accordingly.

[bhilburn]

@opes - Wow, this is a really well-done PR. Based on your use of P9k's internal functions and adherence to coding guidelines, I wouldn't have guessed that this was your first PR. Nice work!

As a new feature, we need to merge this into next rather than master to keep things stable. Unfortunately, I can't re-target this PR because it would pull in a bunch of commits from master. So, I tried doing the master merge manually first, and actually triggered several conflicts, at least one of which is in the Ruby segment code.

So, anyway, this is a long way of saying I need to sort this out, and then will merge this into next, hah.

[opes]

Thanks for following up, @bhilburn! Let me know if there's anything I need to do on my end to assist.