Update TODO.md file, add todo task and change type of metakeywords from String to Array

Author: hbakhtiyor

TODO.md

@@ -47,4 +47,17 @@
 *   Add sample data with utility test validation for the schemas.
     For more information about the utility refer to the [link](http://json-schema.org/implementations.html)
 
-*   Rename project to `elasticad-json-schemas`.
+*   Rename project to `elasticad-json-schemas`.
+
+*   Add example samples for each schema definitions.
+    e.g. For `ad` document.
+    ```json
+    {
+      "taxon_id": ObjectId("5280afc77562003afc0e0000"),
+      "title": "Book by Ruby on Rails programming",
+      "description": "Wonderful book written by smarter authors",
+      "type": "FOR_SALE",
+      "placement_period": "2.weeks",
+      "activation_hash": "5280afc77562003afc0e0000"
+    }
+    ```

json-document/ad.json

@@ -51,7 +51,7 @@
     "meta": /* meta data */
     {
       "description":  "<String>", /* Text */
-      "keywords":     "<String>",
+      "keywords":     "<Array>",
       "title":        "<String>"      
     }
   }