Add Slider Control

Fixed marshaller issues with latest test service (which includes a slider).

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #22 from GordonSmith/SLIDER

Add Slider Control
Add Choropleth Counties

Split States and Counties into two different widgets.
Delete ChoroSurface

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Refactor Widget Base Classes

Rename D3Widget to SVGWidget
Add HTMLWidget

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>