The plugin is available from Atlassian Plugin Repository. Alternatively grab the jar referenced above and install manually via Administration Console/Plugins. If you are on Windows and it insists on treating the jar as a zip and open it up right away grab the zip file instead - the jar file you need to upload is inside.
The plugin has no external dependencies.
Usage
Once the plugin has been installed an action "SpaceUnZip" appears on the attachment page. Zip your folders up, attach the file and then click on the action to unzip them into the space.
