Viewing a markdown file in the terminal

Use lowdown to mark the file up appropriately, and pass it to less -R, which supports ANSI colour codes:

mdview () { lowdown -tterm $1 | less -R ; }
mdview README.md

As a fish alias (save to ~/.config/fish/functions/mdview.fish):

function mdview --wraps='lowdown' --description 'View a markdown file'
  lowdown -tterm $argv[1] | less -R
end

This invocation is straight from the lowdown(1) manual.