GlobalKeymap favor most recently declared bindings in case of tie

Just like in CSS, when multiple equally-specific selectors match an
element, we favor the most recently declared one, so keybindings
cascade.

src/atom/global-keymap.coffee

@@ -10,7 +10,7 @@ class GlobalKeymap
     @bindingSets = []
 
   bindKeys: (selector, bindings) ->
-    @bindingSets.push(new BindingSet(selector, bindings))
+    @bindingSets.unshift(new BindingSet(selector, bindings))
 
   handleKeyEvent: (event) ->
     currentNode = $(event.target)