Atom feed generation using Jinja2

Trying to put together an atom feed, using Jinja2 templates. It works quite well currently, does the nice escape using "| escape" feature in Jinja2 for my use.

Things to do, make it better:

1. Develop an atom id for the file, and for entries.
2. Need to find a simple update for updated tag in atom.

Special thanks to @esbullington for his gist, which I tried to emulate in the atom.xml template.