Open Automator

Choose "New Document"

Locate "Run AppleScript" and double-click it

Paste the Applescript code into the box

Save as /Applications/TerminalVim.app

In Finder, select some file you want to open in Vim, e.g. a .rb file.

Hit ⌘I to open the “Get Info” window.

Under “Open with:”, choose TerminalVim.app. You may need to select “Other…” and then browse.

Hit the “Change All…” button and confirm.