Get off off rails-assets

Just moving the things we currently use (and should drop in the ASAP) to vendor/assets

vendor/assets/javascripts/holderjs/test/phantom.js

@@ -0,0 +1,15 @@
+var page = require('webpage').create();
+
+page.onConsoleMessage = function (message) {
+    console.log('Page: ', message);
+};
+
+page.open('index.html', function (status) {
+    console.log(status);
+
+    if (status === 'success') {
+        page.render('phantom.png');
+    }
+
+    phantom.exit();
+});