Scrape Audits from OPM OIG site

My scraper only works for the [audits page](http://www.opm.gov/our-inspector-general/reports/) on the Office of Personnel Management OIG's site. The other documents are scattered and disorganized on the site and I wasn't sure how to go about it.

It defaults to grabbing the most recent year's audits and has a "--since=[year]" option that can go back to a certain year.