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
That opens all manner of problems. @mjuniper and I had discussed using a promise library (Q) to avoid callbacks, but that complicates using this with other frameworks (notably jquery, and dojo which use other promise libs)

Callbacks are somewhat crufty, but they are core to async things in javascript.