slugification initiated; post link corrected; more

fixed broken urlconfs ... by changing their order (!)

[#8]
marginally saner migrations

I am appalled that this ugly three-migration "new nullable field, data
migration, make field non-nullable and unique" maneuver seems to be
necessary to do this simple thing. Thanks to Thomas in
http://stackoverflow.com/a/7226563 for showing me the darkness.
post.pk corrected to post.slug in post template
URL field in post-creation form (doesn't do anything yet)
dynamic slugification as user enters title
user-defined slugs now operational
name-collision checking
date namespace
add slug field to PostFactory; correct tag URLconf regex
repair tagging
repair commenting

(Including plucking the anti-CSRF token into the
commenting-on-a-comment form.)

The reader will note the philosophical stance taken here, that
readable slugs are important for human readers, but URLconfs that
exist to be POSTed to and respond with a redirect can just take a
plain pk.
Merge branch 'slugs_rebasing'