Go straight from create class to new chart.

[toonarmycaptain]

Prompt to allow user to go straight to creating a new chart after creating a class.

Could be done with dialogue, and if user wants to create a chart with the class, call new_graph with optional keyword arg class_name='class_name' that would filter through to assemble_chart_data, which would have something like if not class_name: class_name = select_classlist()

[toonarmycaptain]

GitMate.io thinks a possibly related issue is #14 (Settle on class data format).