custom.css should be after style.css

In oik version 1.6 I’ll be changing the order of the enqueued stylesheets so that the custom.css file comes after your theme’s style.css file. This fix will overcome a minor problem I noted when attempting to override the styling of the default BuddyPress pull down menu. In the current version of oik, the CSS file is loaded before the BuddyPress default file so the CSS overrides don’t work. The definitions in the BuddyPress file take precedence.