Get off off rails-assets

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

vendor/assets/javascripts/momentjs/templates/locale-header.js

@@ -0,0 +1,6 @@
+;(function (global, factory) {
+   typeof exports === 'object' && typeof module !== 'undefined'
+       && typeof require === 'function' ? factory(require('../moment')) :
+   typeof define === 'function' && define.amd ? define(['../moment'], factory) :
+   factory(global.moment)
+}(this, (function (moment) { 'use strict';