Bar graph added.

node_modules/vega-cli/bin/vg2png

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+// Render a Vega specification to PNG, using node canvas
+const {createWriteStream} = require('fs'),
+      render = require('../src/render');
+
+render('png', function(canvas, arg) {
+  const file = arg._[1] || null,
+        out = file ? createWriteStream(file) : process.stdout,
+        stream = canvas.createPNGStream();
+  stream.on('data', chunk => { out.write(chunk); });
+});