Download and add the package to your Packages folder or just clone it there.
cd ~/Library/Application\ Support/Sublime\ Text\ 2/Packages/
git clone git://github.com/andrewfiorillo/pubsyntax.git
Autocomplete and commenting:
Function navigation:
Pub and html:
If you want the colorscheme, you can grab that here: http://github.com/andrewfiorillo/Cupid