notify readers when they're looking at old docs

[chadwhitacre]

I want to use the latest stable release of my project as the default version, and I would like to prominently warn users when they are looking at other versions, including both latest, other branches, and past releases. I want the other versions to still be available in the nav at lower left.

I like something like this (cf. #518):

But a) I'm not sure how to achieve that (I tried unchecking versions that have already been built on the Versions page, and b) old versions aren't linked in the nav in that example.
#555 might be related.

[ericholscher]

This is implemented now. You can see it here: http://flask.readthedocs.org/en/0.1/