add WTFPL

This project doesn't have a license & public domain doesn't exist in
many countries. So I choose a license as close to public domain as
possible, and as simple as possible.
this rule cannot be applied

Specifying a rule for lines that exceed 80 chars contradicts the rule
that lines cannot exceed 80 chars, so the former rule is never useful.
Having a line where the rule applies would break the 80 char rule.
bold shouldn't be capatalized
add some periods and re-flow text for 80-char rule
fix instances where post-header newline is missing