PapaParse: Papaparse not working with browserify

Because of the way browserify module’s work, the scope here is not actually window.

While the this keyword is good for keeping everything inclosed, the papaparse library uses the window.postMessage function, so the anonymous function must return window, otherwise you run into errors.

Before I submitted a PR, I wanted to get @mholt’s opinion on if this is the right move here.