removed reference to button color and gradient

Changed the wording to reflect the default button's new look since it's no longer grey and doesn't have a gradient. I'd say this new wording isn't ideal and needs something a bit more, well, descriptive.
removed extraneous space
remove .btn-group

The example doesn't use .btn-group and adding the class causes "bad things to happen," as the saying goes.

http://jsfiddle.net/josephtate/g6AWF
Merge pull request #9996 from jodytate/master

changed description of default button