Expose the "resize()" function of c3 to angular

Hi Max, 

I'd like to expose the resize() function from c3; I need to call it when resizing the div which contains the chart but not resizing the window itself. 

Unfortunately, I could not figure out how to test this functionality. I don't know how to get the "chart" property of the directive in the test. If I could, I would maybe test it like this:

      describe('. resize', function () {
        it('- Resize on chart should be callable from outside.', function () {

          directiveScope.chart = {resize: angular.noop};
          spyOn(directiveScope.chart, 'resize');
          elementScope.options.resize();

          expect(directiveScope.chart.resize()).toHaveBeenCalled();

        });
      });

Where directiveScope is the scope of the Directive and elementScope is the scope of outside.