Render content of external markdown file

I'd like to use page metadata to make Gitit render the external markdown content like its own page. Something like:

```
---
url: http://example.com/raw/tip/README.md
...
```

I know now that you can make Gitit show content of external file as it would be its versioned file, simply just by [creating symlink](http://stackoverflow.com/questions/39394748/how-to-serve-external-markdown-files-via-gitit-wiki) to that file and committing it to Gitits' VCS.
It would be awesome if you could do something similar to render external (on the web) content.