Change the directory of Bootstrap from '_assets' to static 'assets'.

assets/vendor/bootstrap/js/transition.js

@@ -0,0 +1,48 @@
+/* ========================================================================
+ * Bootstrap: transition.js v3.1.1
+ * http://getbootstrap.com/javascript/#transitions
+ * ========================================================================
+ * Copyright 2011-2014 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * ======================================================================== */
+
+
++function ($) {
+  'use strict';
+
+  // CSS TRANSITION SUPPORT (Shoutout: http://www.modernizr.com/)
+  // ============================================================
+
+  function transitionEnd() {
+    var el = document.createElement('bootstrap')
+
+    var transEndEventNames = {
+      'WebkitTransition' : 'webkitTransitionEnd',
+      'MozTransition'    : 'transitionend',
+      'OTransition'      : 'oTransitionEnd otransitionend',
+      'transition'       : 'transitionend'
+    }
+
+    for (var name in transEndEventNames) {
+      if (el.style[name] !== undefined) {
+        return { end: transEndEventNames[name] }
+      }
+    }
+
+    return false // explicit for ie8 (  ._.)
+  }
+
+  // http://blog.alexmaccaw.com/css-transitions
+  $.fn.emulateTransitionEnd = function (duration) {
+    var called = false, $el = this
+    $(this).one($.support.transition.end, function () { called = true })
+    var callback = function () { if (!called) $($el).trigger($.support.transition.end) }
+    setTimeout(callback, duration)
+    return this
+  }
+
+  $(function () {
+    $.support.transition = transitionEnd()
+  })
+
+}(jQuery);