Beta banner copy revisions

:fork_and_knife: 

@brettchalupa - I was running on fumes yesterday afternoon and started playing around with the beta banner copy. It's a bit wordier than before, but if you like the direction, perhaps we can whittle it down to something more compact.

One thing I tried and then scrapped was putting the second paragraph in the right-hand column in a third column. However, I could not think of a heading for such a column.

ETA: I also styled the links to contrast with the text a bit more. It could very well just be me that likes that sort of contrast, and I wouldn't push back if you or @danvolkens vetoed such a change.

![beta banner](https://cloud.githubusercontent.com/assets/35545/2916263/4ce56e9e-d6b9-11e3-925d-3eddd0f6a248.png)