use Color attributes for range slider handles

Author: etpinard

src/components/rangeslider/constants.js

@@ -44,8 +44,6 @@ module.exports = {
 
     handleWidth: 4,
     handleRadius: 1,
-    handleFill: '#fff',
-    handleStroke: '#666',
     handleStrokeWidth: 1,
 
     extraPad: 15

src/components/rangeslider/draw.js

@@ -482,8 +482,8 @@ function drawGrabbers(rangeSlider, gd, axisOpts, opts) {
         x: 0,
         width: constants.handleWidth,
         rx: constants.handleRadius,
-        fill: constants.handleFill,
-        stroke: constants.handleStroke,
+        fill: Color.background,
+        stroke: Color.defaultLine,
         'stroke-width': constants.handleStrokeWidth,
         'shape-rendering': 'crispEdges'
     };