Amtrak OIG scraper

Here's a scraper for the Amtrak OIG. The scraper can handle page limits and year ranges, but doesn't as of yet handle types/categories. The Amtrak OIG has a ton of document categories, (even one with only one document) and I wasn't sure if I should start making up my own values for the 'type' field.

I happily waive all copyright and related rights to this code.