Changes:
- add +fold--ts-fold-p which only checks if the feature is around
- add ts-fold into +fold/toggle, +fold/open, +fold/close
- update doc strings
This fixes an issue where zm wasn't auto-loading hideshow and
hs-minor-mode, preventing it from working.
Also reveals +fold/* commands to non-evil users (but as of yet, there
are still no non-evil keybinds for it).