Fix: '.md' to '.html' with anchors (fixes #1415)

Markdown documentation can now reference another markdown file with an anchor and it will work for the site along with github.
ex. `working-with-rules.md#rule-unit-tests`
You're correct - this was broken from the start, but the pattern was unique enough that we didn't notice (I think it only ended up matching one place on the site). We should get that fixed up.