text: Title: Group acquisition function and optimizer arguments
  Body: The number of arguments that need passing around is increasing, sooner or later we will start having collisions, and it is getting unwieldy.
  
  [Suggestion](https://github.com/scikit-optimize/scikit-optimize/pull/234/files#r95050797) is to replace them by `acq_func_kwargs` and `acq_optimizer_kwargs` instead of (`n_points`, `n_restarts_optimizer`, `xi`, `kappa`).
  
  Maybe start this before #115 