Don't assign window.jQuery in jasmine-jquery.js helper

I wrap it in a function wrapper to ensure that the assignment
`var jQuery` doesn't end up assigning a window global.

spec/spec-helper.coffee

@@ -2,7 +2,7 @@ require 'window'
 window.setUpEnvironment()
 
 nakedLoad 'jasmine-jquery'
-$ = require 'jquery'
+$ = jQuery = require 'jquery'
 _ = require 'underscore'
 Keymap = require 'keymap'
 Config = require 'config'

vendor/jasmine-jquery.js

@@ -1,4 +1,5 @@
-jQuery = require('jquery');
+(function(jQuery) {
+
 jasmine.JQuery = function() {};
 
 jasmine.JQuery.browserTagCaseIndependentHtml = function(html) {
@@ -174,4 +175,4 @@ beforeEach(function() {
 afterEach(function() {
   jasmine.JQuery.events.cleanUp();
 });
-
+})(require('jquery'));