clean up awk program

[vijithassar]

The awk portion of this tool began as an adaptation of @trauber's gist that was simply reformatted across multiple lines for the sake of clarity, but it has changed a bit now that it has the ability to comment out the Markdown instead of strip it. This should be reworked and cleaned up, most notably to use native awk variables when possible instead of treating the awk program code as a string and using Bash variable expansion to change it.

This should be implemented before the identifiers proposal.