File paths for Sublime Text 3 on OS X:
~/Library/Application Support/Sublime Text 3/Packages/User/add_to_project.py
~/Library/Application Support/Sublime Text 3/Packages/User/Default (OSX).sublime-keymap
Credit to https://www.sublimetext.com/forum/viewtopic.php?f=6&t=13021 for relevant resources I used to put this together.