Update mdp_planner.py

quick fix for current nav bugs
back to using topological navigation special modes

for learning and policy execution
Merge pull request #51 from hawesie/hydro-devel

Working around the time comparison bug some more.
small improvement in policy execution;
updated robbloging
reads mdp with states labels initial and target at the same time
Merge pull request #52 from BFALacerda/hydro-devel

small edits to mdp stuff
Adding support for giving the robot days off.
Added days and dates off for the routine.

Not the most efficient way to bring in the check, but this part is tested for this kind of behaviour.