Scoutfile used at Float developed around the concepts presented in @SlexAxton's post: http://alexsexton.com/blog/2013/03/deploying-javascript-applications/

scout.js

// ScoutFile - MIT (c) @philip_roberts
// This file should be as close to the top of you html as possible, and be cached for
// a short time.
//
// The configurable section should define a `loadScripts` function
// which uses addCssTag and addScriptTag to load in the required
// scripts. loadScripts should also call onScriptsLoaded when it's
// imported all the scripts it needs (probably in the addScriptTag onDone callback).
//
// addCssTag(url) - injects the css file at url into the page
// addScriptTag(url, onDone) - injects the javascript file at url into the page, 
//                             and calls onDone when it's been imported
//
// The scoutfile also exposes a $R function on window. You can use this to define
// callbacks that will not be called until `onScriptsLoaded` is called, ie:
//
// $R(function() {
//   $(function() {
//     alert('hi');
//   })
// })
//
// will not be run until the script tags have all loaded (which will presumably 
// include jQuery). This prevents the script which depends on jQuery running before
// $ has been loaded

// NB: this example will be compiled by grunt, where the deployEnv and buildNumber values are interpolated at grunt-time.

(function() {
  //Configurable
  var base, loadScripts; 

  base = 'https://<your subdomain>.cloudfront.net/envs/<%= deployEnv %>/b<%= buildNumber %>/';
  loadScripts = function() {
    addScriptTag(base+'app-min.js', onScriptsLoaded);
    addCssTag(base+'app-min.css');
  };


  //Private
  var firstTag = document.getElementsByTagName('script')[0],
      callbacks = [],
      scriptsLoaded = false,
      $R,
      onScriptsLoaded;

  window.$R = $R = function(cb) {
    if (scriptsLoaded) cb();
    else callbacks.push(cb);
  };

  onScriptsLoaded = function(cb) {
    for (var i=0,ii=callbacks.length; i<ii; i++) {
      callbacks[i]();
    }
    scriptsLoaded = true;
  };

  function addScriptTag(f, cb) {
    var tag = mkTag('script');
    tag.src = f;
    tag.type = 'text/javascript';
    addOnloadHandler(tag, cb);
    putTag(tag);
  }

  function addCssTag(f, cb) {
    var tag = mkTag('link');
    tag.type = "text/css";
    tag.rel = "stylesheet";
    tag.href = f;
    putTag(tag);
  }

  function mkTag(t) {
    return document.createElement(t);
  }

  function putTag(tag) {
    firstTag.parentNode.insertBefore(tag, firstTag);
  }

  function addOnloadHandler(tag, cb) {
    if (!cb) return;

    if (typeof tag.addEventListener !== "undefined") {
      tag.addEventListener("load", cb, false);
    } else {
      tag.onreadystatechange = function() {
        script.onreadystatechange = null;
        ieLoadBugFix(script, cb);
      };
    }
  }

  function ieLoadBugFix(scriptEl, cb) {
    if (scriptEl.readyState=='loaded' || scriptEl.readyState == 'completed') {
      cb();
    } else {
      setTimeout(function() { ieLoadBugFix(scriptEl, cb) }, 100);
    }
  }

  loadScripts();
})();