Add National Credit Union Administration

A few things to note:

- We are not scraping [Material Loss Reviews](http://www.ncua.gov/about/Leadership/CO/OIG/Pages/MaterialLossReviews.aspx), but they all appear under the audit reports section so we should be good.
- Not currently scraping [Performance and Strategic Plans](http://www.ncua.gov/about/Leadership/CO/OIG/Pages/PerformanceStrategicPlans.aspx). It looked like it would be a bit annoying and I couldn't remember if we cared much about these types of reports. If they would be useful, I can add code that just associates them with November 1 of the respective years.
- Not currently scraping [FOIA](http://www.ncua.gov/about/Leadership/CO/OIG/Pages/FOIA2012.aspx). There is only one report and I am confused about the url structure. It is easy enough to add this page and hope subsequent reports are added here, but I'm a bit skeptical.