Added random state feature

This adds the functionality of getting the mini batches in the same order if the user provides a random state object. Depends on https://github.com/BRML/climin/pull/22
The only that is needed is that the `random_state` attribute of a model is initialized as what we want (which by default is `None` in all models). Done the example for `Mlp`.

Included some test cases for this for the `Mlp` model.