Make scale's 'breaks' / 'labels' parameters understand dict of breaks as keys and labels as values.

[alshan]

At the "Titanic" example nice to use dict:

embark_dict = dict(C='Cherbourg', Q='Cobh', S='Southampton')

as 'breaks' / 'labels' - need to consult ggplot2 docs to figure out which parameter is most suitable (or maybe both?)