Allow to work in non-browser env

‘window’ is specific to browser environments. ‘this’ (the global object is the default ‘this’ value) allows it to work in non-browser environments other than node.

src/convnet_export.js

@@ -1,7 +1,7 @@
 (function(lib) {
   "use strict";
   if (typeof module === "undefined" || typeof module.exports === "undefined") {
-    window.convnetjs = lib; // in ordinary browser attach library to window
+    this.convnetjs = lib; // in ordinary browser attach library to window
   } else {
     module.exports = lib; // in nodejs
   }