Breaking up large code blocks into smaller functions.
Keen.Visualization constructor broken up into smaller class functions.
Added Keen.Dataviz class.

Created new Keen.Dataviz class and using it inside the Keen.Visualization constructor. This allows us to keep the same API that but allow much greater accessibility under the hood.
Moving towards chained, composably style of API for Keen.Dataviz
Cleaning up options object.
Syntax fix.