This should work for TextMate and anything that's compatible (e.g. Sublime Text).

Copy the tmLanguage files into the Packages/User folder in your Sublime Text configuration folder.

These folders are located at the paths shown below. Replace 2 with 3 if you're a ST3 user.

• OS X: ~/Library/Application Support/Sublime Text 2
• Windows: %APPDATA%\Sublime Text 2
• Linux: ~/.config/sublime-text-2

Open a .asm file, and choose View > Syntax > Open All ... > Pwntools ....