Adding a new tab called 'lab'

IMHO it could be nice to have a new tab called 'lab' on the top bar of MetaCPAN that would lead to a page listing various experimental feature.

This pull-requests contains the lab page and an experimental feature:

Listing *all* the dependencies of a module together with the latest release date. This can help a module author or user see when the dependencies get updated.

I know the feature is far from being presentable, but before I go on working on it, I'd like to get your feedback.