border-right on middle button on buttonset()

[reyx]

I have update the line 356 on minified version:

.addClass("ui-corner-right").end().end()

With this:

.addClass("ui-corner-right").end().not(':first, :last').css({'border-right':'none'}).end().end()

To remove extra border on buttonset()

[Scott González]

This change would result in poor styling for active buttons. Also, it's not correct to define styles in JavaScript.