clean up PolicyIteration._evalPolicyIterative argument checking
clean up PolicyIteration._evalPolicyIterative argument checking

silgon/pymdptoolbox,sawcordwell/pymdptoolbox,yasserglez/pymdptoolbox,McCabeJM/pymdptoolbox,McCabeJM/pymdptoolbox,sawcordwell/pymdptoolbox,yasserglez/pymdptoolbox,silgon/pymdptoolbox