A bit of user-friendlyness

This release bring some convenient functionalities.

Added

• You can see the best score and best dimensions updating in
  trials_and_errors_optimization.

Changed

• The optimizers tests are 5 times quicker (~1 second now) and raise less
  false positive.
• The sidebar in the documentation make navigation easier.
• A bit of reorganization in optimizers, it should not affect users.