Redesign form focus state to use blue border and white background rather than yellow.

h/static/styles/forms.scss

@@ -80,12 +80,12 @@
   }
 
   &:focus, &.js-focus {
-    outline: none;
-    border-color: $focus-yellow-dark;
-    background-color: $focus-yellow;
+    background-color: #FFF;
+    border-color: #51A7E8;
+    box-shadow: 0px 1px 2px rgba(0, 0, 0, 0.075) inset, 0px 0px 5px rgba(81, 167, 232, 0.5);
 
     @include placeholder {
-      color: $focus-yellow-darker;
+      color: $gray;
     }
   }
 }