Make Person.student a deferred column_property.

This makes it possible to (optionally via undefer) pull it in as part of a
ORM Person.query instead of having to build a full custom select clause.
Use io.BytesIO instead of cStringIO.
Prefer google CDN for jQuery, with local fallback.
Take company into account when deciding student/adult.
README.markdown: Reformat text a bit.
Add font settings.
Don't run setup.py install from fabfile.
Fabfile: Use system site packages in virtualenv setup.