Squashed commit of the following:

commit bab205dff6d602014c6bc186fc76392b808dc604
Author: Chris Tweney <chris@media.berkeley.edu>
Date:   Mon Apr 7 10:52:17 2014 -0700

    Point at production Calcentral stats

commit c608f533bfddf20c3b606be4bf9e3103425e23d6
Author: Chris Tweney <chris@media.berkeley.edu>
Date:   Thu Mar 20 08:26:04 2014 -0700

    Add a warning state color, and make HotPlate stats and LiveUpdate stats use it

commit 441bf59c61ec504cd8c7be87158a4c93d694f2ac
Author: Chris Tweney <chris@media.berkeley.edu>
Date:   Fri Mar 14 15:49:30 2014 -0700

    Better way of defaulting STATS_URL

commit 522822314194c79a7b8ff3fdea8fe826539842a6
Author: Chris Tweney <chris@media.berkeley.edu>
Date:   Fri Mar 14 15:40:02 2014 -0700

    Parameterize STATS_URL and make display nicer for null data

commit 184b31717ad235db19825abffdbff0c33c121901
Author: Chris Tweney <chris@media.berkeley.edu>
Date:   Fri Mar 14 13:27:54 2014 -0700

    Add stats for HotPlate and LiveUpdates (currently pointed at localhost)
Use span instead of a, and add var where needed
Merge pull request #2 from ctweney/hotplate_stats_squash

Add HotPlate and LiveUpdates stats