Add support for grizzl
Update Carton deps
Add a grizzl screenshot
Clean up completion options section
Fix a typo
Make grizzl optional dependency

Notice user if grizzl is set as completion system but not installed
Merge pull request #140 from ptrv/make-grizzl-optional

Make grizzl optional dependency
add fossil support
Merge pull request #141 from kartoffelbrei-mit-muskatnuss/master

Add fossil support
Mention ido-flx in the README
Clean up and extend the README a bit