Add more command-line tools

[fperez]

The key one here is really the man pages support, please LMK if you prefer that I separate b50ec74 from the other commit(s). The others were just me adding various tools as I think more long-term, but then I ran into this for every single command:

jupyter-fernando-2eperez[~]> man ls
No manual entry for ls
See 'man 7 undocumented' for help when manual pages are not available.
jupyter-fernando-2eperez[~]> man bash
No manual entry for bash
See 'man 7 undocumented' for help when manual pages are not available.

and I realized we need the actual content of man pages, not just the man command :)

No big rush though, I can do without for now.

And sorry I didn't catch all these issues earlier!! Please don't think any of this is urgent - I deeply appreciate the team's work and I'm totally fine now with the setup we have. This is now polish for the long run, not a critical need.

[yuvipanda]

@fperez I really appreciate the PRs you are making :)

I opened jupyterhub/repo2docker#909 in repo2docker to allow us to use newer base images, maybe I should pick that up again...

[fperez]

Certainly @yuvipanda - I'm delighted with how the system is shaping up, and I'm trying to really "make it my home" so we can reliably use it for all daily work. Your team's recent improvements are phenomenal and are getting us there, I just try to do my small part :)

We're getting to a pretty awesome setup, so this is now polish on top. Exciting!