Make component drag-and-drop a little nicer

cms/static/coffee/src/views/unit.coffee

@@ -42,6 +42,11 @@ class CMS.Views.UnitEdit extends Backbone.View
     @$('.components').sortable(
       handle: '.drag-handle'
       update: (event, ui) => @model.set('children', @components())
+      helper: 'clone'
+      opacity: '0.5'
+      placeholder: 'component-placeholder'
+      forcePlaceholderSize: true
+      axis: 'y'
     )
 
     @$('.component').each((idx, element) =>

cms/static/sass/_unit.scss

@@ -87,6 +87,10 @@
         }
       }
 
+      &.component-placeholder {
+        border-color: #6696d7;
+      }
+
       .xmodule_display {
         padding: 40px 20px 20px;
       }