Homebrew now installs nginx in /usr/local/bin/

Hey thanks for this repo! It saved me a lot of time getting nginx set up correctly. :+1: 

I ran into a small issue with the incorrect path being set in the `org.nginx.plist`. It seems that brew now installs it in `/usr/local/bin` instead of `/usr/local/sbin`. It took me a while to figure out the problem, but I finally thought to monitor the launchd logs in the Console.app.