clean code
update README.md
TODOs 001 #1: Let "sanitize" mode decide whether spaces in the name of code language should be replaced with a dash.
fix README.md
enhance helper function `pad` with a better algorithm
TODOs 002 #2 Change the syntax of macros, links, and auto-links.
Macros use `<[ ]>` instead of `[[ ]]` now.
Links with empty URL or reference name can omit the the colons `:`.
Automatic links use `[[ ]]` instead of `[ ]` now.
update
update