revert a couple of css changes

Author: toddjordan

app/styles/components/_highlight.scss

@@ -43,6 +43,7 @@
   table {
     border: none;
     margin: 0;
+    table-layout: auto;
     overflow: auto;
     width: 100%;
     z-index: auto;
@@ -104,7 +105,6 @@
     @include size(52px 20px);
     background: 0 0 no-repeat;
     background-size: 52px 20px;
-    background-color: $code-background;
     z-index: 9;
   }