Update intro.rst

added a quick how-to.
Update intro.rst

Tried to make it quick and easy to get started.
Update intro.rst
Update intro.rst
Update intro.rst
Update intro.rst
Update intro.rst
Update intro.rst
changed get_paper template to avoid author db queries for Rec, Post, Reply
Merge branch 'patch-3' of https://github.com/johncarlosbaez/spnet into tmp
more intro doc fixes: addressed question from John; clarified sign-in; various minor fixes