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
Can we encapsulate this within the `create` method. Internally it creates and object for return, while `getJson` is async and will populate that object.

```javascript
Cedar.create(chartType, options, function() {
   var _chart = {};
   if(chartType.is_a?(Url)) { // pseudo
     Cedar.getJson(chartType, function(err,template){
        _chart = Cedar.bind(template, options.url, options.mappings);
     });
   } else { // it's an inline templated-Vega object
        _chart = Cedar.bind(chartType, options.url, options.mappings);    
   }
});

// So the actual usage is extremely simple and doesn't require dev to setup callbacks/errors/etc.

var mychart = Cedar.create("/path/to/bar.json", {url: "FeatureServer/0", mappings: {count: "TOTAL_STUDENTS", group: "FACUSE"});

mychart.show("#students-div");
```
I know there are issues with this in callbacks and checking if the object has been populated by the remote JSON.