added max' and min', plus the start of a major refactor
event-demo.hs - initial LIstT refactor
src/demo-event.hs is latest working version of the ListT approach.
src/demo-event-arrow.hs is the old (and still working) Edge version.
Merge pull request #3 from tonyday567/listt-refactor

Listt refactor
snapshot to revert to previous
minor changes