Upgrade gitbook to 2.1.0
Upgrade gitbook to 2.1.0

beni55/scalacss,Voltir/scalacss,beni55/scalacss,japgolly/scalacss,japgolly/scalacss,Voltir/scalacss,LMnet/scalacss,Voltir/scalacss,LMnet/scalacss,beni55/scalacss,LMnet/scalacss