Add new search terms: ada, bsd, golang, linux, and unix
Add version control software to the search terms
Add support for HTML output
Remove the options list from the file comment

It was already out of sync with the actual arguments the program uses
and accepts.  It is easier for users to simply run the program with
the ‘--help’ option than look at the source code as a manual.
Document the use of ‘--help’ in the README
Bump the program to version 2.0

This is a change in the major version number because previous patches
introduced the ‘--output’ command-line argument, replacing what used
to be a positional argument.  That means argument lists that were
valid for version 1.0 are not guaranteed to work anymore.  Thus the
major version bump.