Defining window globally to stop jshint errors. Fixes #504. Fixes #506.

With the recent move to the [browserified][browserify] flavor of [jshint][], it introduced an error since one of the node modules it depended on was expecting to be run in the browser (i.e. it was looking for `window` to be defined).

Unfortunately, we are running the browserified version in node. As a result, I have defined `window` on the `node` `global` which stops the error in its tracks.

P.S. It would be great to know why we are using the browserified version and not a node_module. I am guessing for portability but the same could be gained from saving node_modules to the repository.

[browserify]: http://browserify.org/
[jshint]: http://jshint.org/