v0.6.0 release

• Adds score in playmode (current and previous scores)
• Playmode now incorporates lights off directly (in examples try: python visualizeArena.py configs/lightsOff.yaml)
• To simplify the environment several unnecessary objects have been removed see here
• Several object properties have been changed also here
• Frames per action reduced from 5 to 3 (i.e.: for each action you send we repeat it for a certain number of frames
  to ensure smooth physics)
• Add versions compatibility check between the environment and API
• Remove step_number argument from animalai.environment.step