This installation is running on WebFaction (using their automated installer), and I often forget how to do minor version bumps.

From Craig Butcher, whose site goes up and down:

1. Jump the directory where Ghost is installed -
   cd ~/webapps/appname/ghost
2. wget the newest release and unzip it - unzip -uo ghost-0.6.5.zip
3. Update npm - ../bin/npm install --production (and don't worry if you get a warning that forever should be installed globally with -g - WebFaction already did this for you)
4. Restart Ghost - ../bin/stop && ../bin/start