If AMD is available, install the plugin

[wvl]

If we're in an AMD environment, wouldn't it make sense to just install the plugin rather than return it? In other words, is there a use case where we require 'chai-jquery' but don't want it installed by default?

I would have expected this:

diff --git a/chai-jquery.js b/chai-jquery.js
index f29f2b1..aa8f693 100644
--- a/chai-jquery.js
+++ b/chai-jquery.js
@@ -5,10 +5,10 @@
     module.exports = chaiJquery;
   } else if (typeof define === "function" && define.amd) {
     // AMD
-    define(['jquery'], function ($) {
-      return function (chai, utils) {
+    define(['jquery','chai'], function ($,chai) {
+      chai.use(function (chai, utils) {
         return chaiJquery(chai, utils, $);
-      };
+      });
     });
   } else {
     // Other environment (usually <script> tag): plug in to global chai instanc