Adressing issue 196 and 185

[BDonnot]

• [FIXED]: Unable to run l2rpn_neurips_2020_track1_small using Rllib integration code  #196 an issue related to the low / high of the observation if using the gym_compat module. Some more protections are enforced now.
• [FIXED]: Unable to run l2rpn_neurips_2020_track1_small using Rllib integration code  #196 an issue related the scaling when negative numbers are used (in these cases low / max would be mixed up)
• [IMPROVED]: on windows at least, grid2op does not work with gym < 0.17.2 Checks are performed in order to make sure the installed open ai gym package meets this requirement (see issue Add minimal gym version in grid2op after gym_compat module (otherwise it crashes) #185 )
• [IMPROVED] the seed of openAI gym for composed action space (see issue https://github.com/openai/gym/issues/2166): waiting for an official fix, grid2op will use the solution proposed there sampling from spaces.Tuple yields non-random behavior openai/gym#2166 (comment) )

[BDonnot]

if tests pass this looks good