Extension sets loaded

src/atom/extension.coffee

@@ -1,12 +1,18 @@
+# Extension subclasses must call super in all overridden methods.
 module.exports =
 class Extension
-  pane: null
+  loaded: false
 
   constructor: ->
     console.log "#{@constructor.name}: Loaded"
 
-  storageNamespace: -> @constructor.name
-
+  # `startup` should be called by you in Extension subclasses when they need
+  # to appear on the screen, attach themselves to a Resource, or otherwise become active.
   startup: ->
+    @loaded = true
 
+  # `shutdown` shuold be called by you in Extension subclasses when they need
+  # to be remove from the screen, unattach themselves from a Resource, or otherwise become
+  # inactive.
   shutdown: ->
+    @loaded = false