Update font-weight mixin
Update font-weight mixin

jjackson21/my_new_site,AlvaroR156/middleman-inuit-slim,startae/middleman-startae,startae/middleman-startae,kandebonfim/keep-talking-and-nobody-explodes,kandebonfim/keep-talking-and-nobody-explodes,romulomachado/middleman-startae,jjackson21/my_new_site,startae/middleman-startae,AlvaroR156/middleman-inuit-slim,kandebonfim/keep-talking-and-nobody-explodes,AlvaroR156/middleman-inuit-slim,romulomachado/middleman-startae