On error, success class is not removed

[flexchar]

Hi,

been using the success class showvalid feature and it appears that if an input field from valid goes to invalid success class is still left on the input group container.

References issue #18

Please note how the tick is still there. It visually represents that the class has not been removed from the input group container element.

Otherwise, pretty good work. :)

[Mevrael]

Sorry for delay and thanks for submitting a bug report. Nothing critical here and PRs always welcome :)