Add example usage next to each mixin, improve opacity mixin, add some REM mixins using LESS's pattern matching feature
Add example usage next to each mixin, improve opacity mixin, add some REM mixins using LESS's pattern matching feature

REM:
.rem(font-size, 16)
.rem(line-height, 16);
.rem(margin, 16);

TryKickoff/kickoff,fredericksilva/kickoff,PatrickEifler/kickoff,fredericksilva/kickoff,legomushroom/kickoff,contra/kickoff,PatrickEifler/kickoff,TryKickoff/kickoff