Adding SubToMe support and fixing feed

Eric,

I hope you're doing very well! I'm still looking forward to see what you're working on these days and excited that it seems to involve so much JS :)

This PR has 2 commits: one adds SubToMe support to your feed icon. You can try it out on [USV.com](http://www.usv.com/) for example. I'd love to get your feedback on SubToMe.

The 2nd commit includes a fix to the timestamps in your feed. Even though `.isoformat()` returns a valid format, Atom feed should not include the ms part that is generated by `.isoformat()`.

Let me know what you think!