Abstract data dereferencing

In order to better facilitate reusability, provide an interface for
working with chart data. With it, chart consumers are able to define the
"shape" of their data. Allow consumers to explicitly opt out of this
behavior for situations that require runtime optimization (i.e. large
datasets, frequently-updating charts, or low-powered devices).
Fix bug in dataAttrs inheritance logic

Account for charts that extend other charts without declaring additional
data attributes.
Do not map non-array-like data

This is a hack to support using mixins for multiple data series. I can't
think of a better solution at the moment
Update examples

They work! But the hybrid chart relies on a hack (see previous commit)
Begin solving data attrs problem?!
Use external library for data mapping
Remove unecessary branch

All charts define a `dataAttrs` array.