Regression, ensure background of containers is white when pageskins are present

Adds background colour of white if a pageskin is present.

Although most pageskins are correctly formatted sometimes they aren't, this removes the risk.

Tricky to do a before and after with a skin but if you apply background-color instead you can see the issue, (used black below.)

Before;
![screen shot 2014-11-24 at 10 26 04](https://cloud.githubusercontent.com/assets/1303616/5163508/51feb248-73c4-11e4-85f6-eb5c4d9196e0.png)

After;
![screen shot 2014-11-24 at 10 25 17](https://cloud.githubusercontent.com/assets/1303616/5163512/59fdeb94-73c4-11e4-846b-af7fa0c2df0d.png)