Merge pull request #737 from MITx/feature/tomg/discussion-read

darker background for read posts

lms/static/sass/_discussion.scss

@@ -1110,10 +1110,14 @@ body.discussion {
         color: #333;
       }
 
-      &.read .title {
+      &.read {
+        background: #f2f2f2;
+
+        .title {
           font-weight: 400;
           color: #737373;
         }
+      }
 
       &.resolved:before {
         content: '';