Enable overflow in Layout in certain Layout configurations
Enable overflow in Layout in certain Layout configurations

Back-porting un-applied upstream fix google/material-design-lite#4180,
fixing failure of config.mode == Scrolling on mobile.

Fix #122.

vipentti/elm-mdl,hakonrossebo/elm-mdl,vipentti/elm-mdl,aforemny/elm-mdc,hakonrossebo/elm-mdl