* Uses classes prototype instead of their aliases
- Class chart was moved to its own script.
- Class AxisInternal was moved to its own script. It's only needed by Class Axis
- Definition of Chart removed from core.js
- Definition of AxisInternal removed from axis.js
* Replaces aliases of Class prototypes
- Alias c3_chart_fn replaced by Chart.prototype where is due
- Alias c3_chart_internal_fn replaced by ChartInternal.prototype where is due
- spec/data.convets.js renamed to spec/data.convert-spec.js for clarity
* Fixes Chart.prototype.legend.hide behavior
- It was calling $$.updateAndRedraw({withLegend: true});
- It should call $$.updateAndRedraw({withLegend: false});
* loads *-helper.js and *-spec.js files
* adds tests to improve coverage
restores c3.js and c3.min.js to master version
fixes linter error
* util is a plain collection of functions
* adds test for api.x, drag and util