With thanks to http://superuser.com/a/1171026/39144
It seems like there is an entirely different method for changing the open files limit for each version of OS X! For OS X Sierra (10.12.X) you need to:
- In /Library/LaunchDaemons create a file named limit.maxfiles.plist and paste the following in (feel free to change the two numbers (which are the soft and hard limits, respectively):
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"