1: Install SIMBL (plugin enabler): http://www.culater.net/software/SIMBL/SIMBL.php
2: Install the TerminalTabSwitching.bundle
git clone https://github.com/dabeeeenster/terminaltabswitching
cp -r terminaltabswitching/TerminalTabSwitching.bundle "/Library/Application Support/SIMBL/Plugins"
3: Restart the Terminal app, and enjoy Cmd+[0-9] tab-switching.