Move documentation header down by hard-coding docstart to be taller.

This is more difficult than it should be because the `docstart` has to have
a fixed height because its children take up no actual height within it.

docs/assets/theme-colors.less

@@ -2,7 +2,7 @@
 
 .docstart {
   width: 100%;
-  height: 345px;
+  height: 390px;
   //border-right: 0px solid #22A699;
   //border:0px solid #22A699;
 }