Make the index page not stupid, but not particularly useful either.

lms/static/coffee/src/discussion/discussion_router.coffee

@@ -11,7 +11,8 @@ class @DiscussionRouter extends Backbone.Router
       @nav.render()
 
   allThreads: ->
-      true
+    # TODO: Do something reasonable here
+    $(".discussion-column").html("No thread selected.")
 
   setActiveThread: =>
     if @thread

lms/static/sass/_discussion.scss

@@ -844,6 +844,7 @@ body.discussion {
     background: #fff;
     box-shadow: 0 1px 2px rgba(0, 0, 0, .05);
     width: 68%;
+    min-height: 500px
   }
 
   .discussion-article {