Change order of @imports in main.css

[dinaddan]

To actually allow overwriting the look and feel of the default grails docs (green skin) using custom.css it should be imported as last one (after skin.css)

[bluesliverx]

Sorry, I didn't even really see this until now. This plugin needs major overhaul, and I'm not sure how quickly I'm going to get to it. I will see what I can do about doing this small fix though.