Nexus 7 (2013) Won't Boot Normally or into Recovery After Attempted Root
Thank god I figured out how to fix it.

The problem was that I was using software that was meant to root a first gen Nexus 7, and I had the second gen (2013) version. Whoops.

In order to fix it, I downloaded the Unroot/Stock Toolkit from
http://www.androidrootz.com/2013/08/nexus-7-one-click-toolkit-for-mac-2013.html

and then downloaded the factory images for the Nexus 7 2013 from Google's site,
https://developers.google.com/android/nexus/images#razor

I then used the Unroot/Stock Toolkit to reload the bootloader and factory image. After this, my Nexus worked fine. I was still able to root, but this time I made sure to use the correct software to do so.