Upgrade to version 1.0.0

[BDonnot]

This release is the first milestone of grid2op, the version 1.0.0

We worked hard on improving the speed of the platform, we added the last feature (the opponent), improve the documentation and fixed dozens of bugs.

The complete changelog:

• [BREAKING] MultiEnv has been renamed SingleEnvMultiProcess
• [BREAKING] MultiEnv has been abstracted to BaseMultiProcessEnv and the backwards compatible interface is now
  SingleProcessMultiEnv
• [BREAKING] the seeds parameters of the Runner.run function has been renamed env_seeds and an agent_seeds
  parameters is now available for fully reproducible experiments.
• [FIXED] a weird effect on env.reset that did not reset the state of the previous observation held
  by the environment. This could have caused some issue in some corner cases.
• [FIXED] BaseAction.__iadd__ fixed a bug with change actions += operator reported in Change bus action += or __iadd__ behavior #116
• [FIXED] obs.simulate post-initialized reward behaves like the environment
• [FIXED] LinesReconnectedReward fixes reward inverted range
• [FIXED] the get_all_unitary_topologies_change now counts only once the "do nothing" action.
• [FIXED] obs.simulate could sometime returns "None" when the simulated action lead to a game over. This is no longer
  a problem.
• [FIXED] grid2op.make will now raise an error if an invalid argument has been passed to it.
• [FIXED] some arguments were not passed correctly to env.get_kwargs() or env.get_params_for_runner()
• [ADDED] Add an agent that reconnects the powerline  #110 Adding an agent that is able to reconnect
  disconnected powerlines that can be reconnected, see grid2op.Agent.RecoPowerlineAgent
• [ADDED] a clearer explanation between illegal and ambiguous action.
• [ADDED] MultiEnvMultiProcess as a new multi-process class to run different environments in multiples prallel
  processes.
• [ADDED] more control on the environment when using the grid2op.make function.
• [ADDED] creation of the MultiMixEnv that allows to have, through a unified interface the possibility to interact
  alternatively with one environment or the other. This is especially useful when considering an agent that should
  interact in multiple environments.
• [ADDED] possibility to use simulate on the current observation.
• [ADDED] the overload of "getattr" for environment running in parallel
• [ADDED] capability to change the powerlines on which the opponent attack at the environment initialization
• [UPDATED] Backend.PandaPowerBackend.apply_action vectorized backend apply action method for speed.
• [UPDATED] Document the feature to reload the IdToAct converter #111 Converter is better documented to be
  more broadly usable.
• [UPDATED] MultiEnv has been updated for new use case: Providing different environments configurations on the same
  grid and an arbitrary number of processes for each of these.
• [UPDATED] Behaviour of "change_bus" and "set_bus": it is no more possible to affect the bus of a powerline
  disconnected.
• [UPDATED] More control about the looping strategy of the ChronicsHandler that has been refactored, and can now be
  more easily cached (no need to do an expensive reading of the data at each call to env.reset)

[BDonnot]

Files changed looks good