Support Redmine 4.x

[guss77]

I'm not sure why, but this plugin doesn't seem to work on my Redmine 4 installation.

The Problem:

I install it according to the instructions, I can see the plugin is loaded and I can configure it. When I enter any CSS into the text box and press Apply, it registers (i.e. I can reload the page and see my changes are retained) but I don't see this CSS applied to any Redmine pages (I specifically want it applied to the Overview and Wiki pages).