The update was a brand new user interface and design so the unfortunately the templates and custom css couldn’t be brought into the new design.  If you are modifying the css only, you can do that in your Rezgo account directly using the Settings > Templates > Rezgo CSS.  Those css changes will carry over into your WordPress site as well.

Bootswatch builds the normal Twitter Bootstrap from the latest version (whatever you install in the bootstrap directory), but also imports your customizations. This makes it easy to use the the latest version of Bootstrap, while maintaining custom CSS, without having to change anything about your HTML. You can simply sway boostrap.css files. Click here for getting more info.