Is it ok for me to edit his answer and include the article in it. I can still preserve the link to his gist.
It depends on the license the article was published under, but usually and by default no. Content on a third party site is not ours to re-use unless the author or copyright holder explicitly say otherwise. (Exception: fair use when quoting, etc.)
In this specific case, you would have to check on the github page under which license or what terms the article was published.
I would ask the author first, though, and explain your reasoning. It's likely he'll see your point and do the copying, or give you express permission to do so.
Edit: I can't find any explicit license on Github, which I find weird but may be by design. All I can see is this general statement, which seems to be referring to code:
We claim no intellectual property rights over the material you provide to the Service. Your profile and materials uploaded remain yours. However, by setting your pages to be viewed publicly, you agree to allow others to view your Content. By setting your repositories to be viewed publicly, you agree to allow others to view and fork your repositories.
make of that what you will.. but I don't read from this a permission to copy & paste an article elsewhere without the author's permission. So you would have to ask them.