Generalize chart width
Introduce chart selection events
Introduce "Rc", a constructor for reusable charts
Generalize default option expansion
Promote `data` attribute

The `data` attribute should be intrinsic (but optional) for all charts
inheriting from Rc.
Fix logic for re-setting BarChart dimensions
Introduce "dataBind" method

This name is more descriptive (and correct) than "_draw", and the
resulting API is much more intuitive--"dataBind" can be specified in the
invocation of "Rc.extend".
Improve API for defining chart "insert" method
Rename source file
Break logic into separate files

In order to better-model how the Reusable Chart template might be used,
separate logic that consumes the chart into dedicated files.