Fixed a bug in taxi where I wasn't letting the put down action actually be taken. Also missed a typo in qlearning. It looks like taxi is sort of insanely painful if you actually use the fuel restriction, which I've made optional by setting '--fuel_loc -1 -1'. But, with fuel enabled there's this very nasty local minimum for the policy where it just avoids doing anything too painful (like incorrectly trying to pick up the passenger) until the fuel runs out.