Gist support

[alexwhittemore]

I love the work! I notice that, trying to use a Gist (https://gist.github.com/alexwhittemore/fb5913c8146ab441e795a13f9ec8d7ea) rather than a commit in a proper repo, I get no output (the frame renders, but no notebook). Digging into nbconvert.php, it looks like you're parsing the URL methodically to extract info about the repo, user, and so on in order to make sure you're always pulling the latest version of the file. It seems to me like that would architecturally preclude the plugin working for Gists?

Additionally, on that Gist page, I see a pretty handy looking "embed" option. It ends up creating a scrolling iframe, which I don't much love, but it's certainly easy and pretty. I suppose another disadvantage vs nbconvert is that it's not auto-updating.

So perhaps for my use-case (I don't want to serve out of a proper repo), either this embedded gist scheme, or raw HTML manually exported from Jupyter Notebook might be more appropriate solutions?