create choropleth-only calc step (can no longer re-use surface's)

Author: etpinard

src/traces/choropleth/calc.js

@@ -0,0 +1,17 @@
+/**
+* Copyright 2012-2016, Plotly, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the MIT license found in the
+* LICENSE file in the root directory of this source tree.
+*/
+
+
+'use strict';
+
+var colorscaleCalc = require('../../components/colorscale/calc');
+
+
+module.exports = function calc(gd, trace) {
+    colorscaleCalc(trace, trace.z, '', 'z');
+};

src/traces/choropleth/index.js

@@ -14,7 +14,7 @@ var Choropleth = {};
 Choropleth.attributes = require('./attributes');
 Choropleth.supplyDefaults = require('./defaults');
 Choropleth.colorbar = require('../heatmap/colorbar');
-Choropleth.calc = require('../surface/calc');
+Choropleth.calc = require('./calc');
 Choropleth.plot = require('./plot').plot;
 
 Choropleth.moduleType = 'trace';