Write a script that generates an overlaid image of the simulated and digitized data

[travs]

Related to #41.

Now that @rayner has completed #40, when we are able to run the simulation with j/pyNeuroML (i.e. #31 is complete) we will be able to do this one.

[travs]

Also note, @rgerkin has done something analogous to this for an ion channel model in in[19] of this notebook