Fix docstrings and rerun

[akapet00]

Hi,

This PR fixes the following issues regarding the recent notebook:

• a few typos in comments;
• a docstring error in hodgkin_huxley_model, should be args : list instead of kwargs : dict, so from this:

def hodgkin_huxley_model(y0, t, A, t_start, t_stop, *args):
    """Return the change in state variables of the neuron.

    Parameters
    ----------
    (...)
    kwargs : dict
        (...)
    """

to this:

def hodgkin_huxley_model(y0, t, A, t_start, t_stop, *args):
    """Return the change in state variables of the neuron.

    Parameters
    ----------
    (...)
    args : list
        (...)
    """

• finally, I did some slight changes in visualization code to be more consistent with previous two notebooks.