also implies that agents are drawn in their old locations, ie from previous timestep

moved test_play.py to use player.py rather than contrived tkplay.py
trying to improve logic around gl.show() show param to renderEnv

added a print.out question : why will an agent not move, once he reach it's destination? May he have to move for passing

Gettingstarteddocs41

Closes #41 and #46

See merge request flatland/flatland!37