Add touch/tap configuration

src/config.js

@@ -214,6 +214,9 @@ c3_chart_internal_fn.getDefaultConfig = function () {
             left: 0
         },
         title_position: 'top-center',
+        //TouchEvent configuration
+        touch_tap_radius : 20,  //touch movement must be less than this to be a 'tap'
+        touch_tap_delay : 500,  //clicks are suppressed for this many ms after a tap
     };
 
     Object.keys(this.additionalConfig).forEach(function (key) {