Remove Parity, Watch, Suspenders, and Rails

* These are great tools, but not critical.
* Some tools should be re-installed right before their use,
  such as Suspenders.
* Restrict Laptop to more fundamental setup.
* Document how to install these in `~/.laptop.local`.
I did mean thoughtbot/dotfiles.

> I think laptop.local is intentionally not in thoughtbot/dotfiles

I wasn't aware of that.