Fix for lefnire's comment on Issue 3327 (no color change on select)

This fix builds on
https://github.com/usernamenumber/habitrpg/commit/750707fbb023a4da972093d04947b9fb701b7ba6

The lack of color change was due to
selected-class:after.background-color being overridden by
.herobox:not(.isUser).background-color. This is fixed by the addition of
!important to that property.

Everything else in the patch is just to add some more "Pow!" to class
selection.