add notes on redis for test readme
add notes on redis for test readme

manueltimita/Windshaft,BHare1985/Windshaft,CartoDB/Windshaft,manueltimita/Windshaft,HydroLogic/Windshaft,wsw0108/Windshaft,manueltimita/Windshaft,CartoDB/Windshaft,HydroLogic/Windshaft,CartoDB/Windshaft,wsw0108/Windshaft,HydroLogic/Windshaft,wsw0108/Windshaft