fix up typos in example module and add extra doctests
fix up typos in example module and add extra doctests

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