Improve a comment.
Add Chart#date_to_x_coordinate.
Retire ChartItem#date_to_x_coordinate.
Simplify Chart#date_to_x_coordinate.
Move y_axis_label x-coordinate calculation responsibility to Chart.
Use accessors instead of @attribute in Chart.
Delegate to Chart#settings to avoid train wrecks.
Add Bar.
Fix list of methods delegated by Chart to Settings.
Replace BarXCoordinates with Bar.
--amend