Set "medium" coverage CSS color scheme to yellow

Fixes #542

Author: JamesMGreene

lib/assets/base.css

@@ -166,19 +166,20 @@ table.coverage td span.cline-any {
 /* dark green */
 .status-line.high, .high .cover-fill { background:rgb(77,146,33) }
 .high .chart { border:1px solid rgb(77,146,33) }
-
-
-.medium .chart { border:1px solid #666; }
-.medium .cover-fill { background: #666; }
+/* dark yellow (gold) */
+.medium .chart { border:1px solid #f9cd0b; }
+.status-line.medium, .medium .cover-fill { background: #f9cd0b; }
+/* light yellow */
+.medium { background: #fff4c2; }
+/* light gray */
+span.cline-neutral { background: #eaeaea; }
 
 .cbranch-no { background:  yellow !important; color: #111; }
 
 .cstat-skip { background: #ddd; color: #111; }
 .fstat-skip { background: #ddd; color: #111 !important; }
 .cbranch-skip { background: #ddd !important; color: #111; }
 
-span.cline-neutral { background: #eaeaea; }
-.medium { background: #eaeaea; }
 
 .cover-fill, .cover-empty {
   display:inline-block;