TODOs

Shorter-term, higher priority

Have render take an obs=None argument that, if not None, would call a special _render_obs function that would plot the state obs rather than the environment's current state. (Is this feasible?)
Allow user to pass in filenames for lots, geometries, environment's parameters, etc.
Make our action and observation spaces subclass gym.Spaces.Dict, and override their .sample() function (and tie this function to the environment's seeding)
Set _EPS_START_HR according to the trips file loaded: use the value of the hour that marks the beginning of the slowest 2-hr window
Generalize discretized time from hour to any arbitrary time unit
Make the action space simpler: have a single request element, with a special value indicating "not providing assignment yet" (self._V?) and another special value indicating "reject this request" (self._V+1?).