GH Examples Working, Api doc, Event Example

Note: There are a lot of files in this but only one change to cedar itself. The others are doc / example / dev artifacts proving out how things can work.

Fixed js and json pathing so examples work at http://esridc.github.io/cedar/

Added example to explore eventing http://esridc.github.io/cedar/examples/scatter-events.html
- currently using the native vega events 

Initial API docs http://esridc.github.io/cedar/api-reference/
- require formatting / styling

Changed "generateChart" method to "compile" - open to ideas on naming this method. http://esridc.github.io/cedar/api-reference/compile.html
Lets talk @ this... I had been designing this assuming that the `.create()` method was used in an app that "designs" charts (aka cypress), and that the `.show()` was used in apps to display the "merged" chart - i.e. en embed, on a homepage, or a story map.

Thus, the assumption that `.create()` would always be handed the chart template, which the app had already fetched via whatever xhr it wanted, or the Cedar.getJson() helper. The net effect is that `.create()` is not async. 

The async comes when the chart is shown - and actually when the vega view object (the chart) is created - I will need to check, but I believe that is when the data is fetched. The `.update()` method on the vega view simply renders.