properly support dependency sort for styles with multiple parents (base + mixins)
properly support dependency sort for styles with multiple parents (base + mixins)

TitoAgudelo/tangram,taylorhxu/tangram,rosamcgee/tangram,taylorhxu/tangram,DHaylock/tangram,xvilan/tangram,xvilan/tangram,TitoAgudelo/tangram,DHaylock/tangram,zerebubuth/tangram,tangrams/tangram,tangrams/tangram,zerebubuth/tangram,DHaylock/tangram,taylorhxu/tangram,rosamcgee/tangram,zerebubuth/tangram,xvilan/tangram,rosamcgee/tangram,ceseale/tangram,ceseale/tangram,ceseale/tangram,TitoAgudelo/tangram