suggestion: state-not mixin

[djurnamn]

when we call the state mixin with name and value there's currently no way of negating it.

for example, instead of doing:

.menu-drawer {
        @include state(drawer, false) {
                display: none;
        }

        @include state(drawer, search) {
                display: none;
        }
}

.search-drawer {
        @include state(drawer, false) {
                display: none;
        }

        @include state(drawer, menu) {
                display: none;
        }
}

maybe we should be able to do something like this:

.menu-drawer {
        @include state-not(drawer, menu) {
                display: none;
        }
}

.search-drawer {
        @include state-not(drawer, search) {
                display: none;
        }
}