Write scatterplot util function

[einbandi]

For the most part, this function should be the same as the one used to construct the plots for the readme. Maybe consider switching from seaborn to pure matplotlib . See if all options are available there and if the custom color palette works as easily. Think about how to export plots to files (ideally with code either before or after the actual plotting function invocation, so that the unaltered plotting code can be used for included in the docs without shenanigans.