Enable 'info' and 'warning' classes on buttons

Includes these classes in export, along with hover effects and disabled
Followup: add bg-hover and border-color for info/warning buttons

Missed this in initial commit
Merge branch 'button-colors' of https://github.com/sekjal/foundation into sekjal-button-colors
Merge branch 'sekjal-button-colors'
Merge branch 'master' of github.com:zurb/foundation