title: Change version of rails
body: <p>I accidentally changed my rails version to 4.0.0. I've tried gem uninstall rails --version=4.0.0.rc1 and install version 3.2.13 but when rails -v it's still version 4.0.0. I then tried gem uninstall rails, which gives me "Successfully uninstalled rails-3.2.13". Thought this was easy to do, but I can't find a simple solution. </p>