Added Design by contract
Added Design by contract

SasView/sasview,SasView/sasview,lewisodriscoll/sasview,SasView/sasview,lewisodriscoll/sasview,SasView/sasview,lewisodriscoll/sasview,SasView/sasview,lewisodriscoll/sasview,lewisodriscoll/sasview,SasView/sasview