Fix nvd3-based charts, babel config is redundant and problematic here,

correct imports.

config/plugins/visualizations/nvd3/nvd3_bar/.babelrc

@@ -1,3 +0,0 @@
-{
-    "presets": ["env"]
-}

config/plugins/visualizations/nvd3/nvd3_bar/package.json

@@ -10,7 +10,6 @@
     "license": "AFL-3.0",
     "dependencies": {
         "@galaxyproject/charts": "^0.1.0",
-        "babel-preset-env": "^1.6.1",
         "backbone": "^1.3.3",
         "bootstrap": "^3.3.7",
         "d3": "^3.4.5",

config/plugins/visualizations/nvd3/nvd3_bar/src/nvd3.js

@@ -1,9 +1,10 @@
 /** This is the common wrapper for nvd3 based visualizations. */
 import * as d3 from "d3";
-import * as nv from "nvd3";
 import * as Backbone from "backbone";
 import * as _ from "underscore";
 
+import "nvd3";
+
 // TODO Disentangle jquery in the future
 /* global $ */