Fix bugs in intra-site linking

* Refactor event handling in controllers to use a method to define
  the hash (and thereby allow inheritance)
* Refactor link handling so that links which should be handled by the
  router can be handled by the base class
* Change the router to throw out controllers for pages which aren't
  on-screen (and thereby avoid a lot of weirdness)

src/scripts/controllers/header_controller.coffee

@@ -28,5 +28,6 @@ module.exports = class HeaderController extends BaseController
 
     # Backbone.View Overrides ######################################################################
 
-    events:
-        'click a.logo': 'onLogoClicked'
+    events: ->
+        return _.extend super,
+            'click a.logo': 'onLogoClicked'