change version number to 4 and Pre-Alpha status
change version number to 4 and Pre-Alpha status

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