Better feeds!

Jeff, here is a pull request which does  2 things:
- add your feed to the <head> so that it's discoverable
- loads [subtome](https://www.subtome.com/#/) when people click on "subscribe". Note that this still allows people to see your feed directly (see the feed icon in the subtome modal), should they want it/know what it is. For the others, it makes things much simpler to follow/subscribe to your feed using the reader's favorite app!