update -dev docs to reflect latest stable version

also updated the release codename, so it doesn't stay with the old "An
Afternoon Hack" one.

After this is merged, it'd be good to build the docs and push them to
http://ipython.org/ipython-doc/dev/ - and I don't believe I have the
permission to do that, but @minrk and @takluyver probably do.
Merge pull request #4228 from ivanov/doc-touchup

update -dev docs to reflect latest stable version