Use @observable annotation instead of @todo observable

apidoc/conf.json

@@ -23,7 +23,6 @@
         "apidoc/plugins/inheritdoc",
         "apidoc/plugins/interface",
         "apidoc/plugins/typedefs",
-        "apidoc/plugins/todo",
         "apidoc/plugins/events",
         "apidoc/plugins/observable",
         "apidoc/plugins/api"

apidoc/plugins/todo.js

@@ -1,14 +0,0 @@
-var util = require('util');
-exports.defineTags = function(dictionary) {
-  dictionary.defineTag('todo', {
-    mustHaveValue: true,
-    canHaveType: true,
-    canHaveName: true,
-    onTagged: function(doclet, tag) {
-      var parts = tag.text.split(' ');
-      if (parts[0] === 'observable') {
-        doclet.observable = '';
-      }
-    }
-  });
-};