Make the missing data message in table modules span the full width

It looks nicer.

Also don't try to float the headers of really short tables (in particular, ones that contain only a no data message)

![screen shot 2014-05-14 at 16 43 17](https://cloud.githubusercontent.com/assets/117398/2973523/840b10b2-db7e-11e3-8c9e-d693ebdc61c5.png)