make sure histograms get a round of bar array-to-calcdata

- require to make colorscale work on histogram traces

Author: etpinard

src/traces/histogram/calc.js

@@ -14,6 +14,7 @@ var isNumeric = require('fast-isnumeric');
 var Lib = require('../../lib');
 var Axes = require('../../plots/cartesian/axes');
 
+var arraysToCalcdata = require('../bar/arrays_to_calcdata');
 var binFunctions = require('./bin_functions');
 var normFunctions = require('./norm_functions');
 var doAvg = require('./average');
@@ -168,6 +169,8 @@ module.exports = function calc(gd, trace) {
         }
     }
 
+    arraysToCalcdata(cd, trace);
+
     return cd;
 };