Use lesspipe if installed
Highlight only the 100th character, not the rest of the line

I think this looks a lot better and I don't have the problem with very
long lines I cannot control losing highlighting.
Remove trailing whitespace when saving
Don't highlight gitcommit overflow extra
Only highlight long lines in insert mode

This should probably remove the markers from buffers that one does not
edit anyway (like the quick fix list).
Add git rebase settings