Don't hardcode slimscroll options. (#1605)

build/js/Layout.js

@@ -130,9 +130,7 @@
 
         // Add slimscroll
         $(Selector.sidebar).slimScroll({
-          height: ($(window).height() - $(Selector.mainHeader).height()) + 'px',
-          color : 'rgba(0,0,0,0.2)',
-          size  : '3px'
+          height: ($(window).height() - $(Selector.mainHeader).height()) + 'px'
         })
       }
     }