require() loads js in strict mode

Main advantage: variables won't accidentally
leak into the global scope.

$ cat gg.js
bad = true

https://img.skitch.com/20110909-kry3pm4ask5qhj5rg43yb37tci.png

src/require.coffee

@@ -45,6 +45,7 @@ exts =
     if not /define\(/.test code
       code = """
         define(function(require, exports, module) {
+          'use strict';
           #{code};
         });
       """