fix Model#update_attributes and add Model#update_attributes!

Author: dks17

docs/tutorials/mongoid-persistence.txt

@@ -108,15 +108,27 @@ examples.
 
    * - ``Model#update_attributes``
 
-       *Update the provided attributes (and any other dirty fields).*
+       *Update the document attributes in the database. Will return true if validation passed,
+       false if not.*
      -
         .. code-block:: ruby
 
-          person.update_attributes!(
+          person.update_attributes(
             first_name: "Jean",
             last_name: "Zorg"
           )
 
+   * - ``Model#update_attributes!``
+
+       *Update the document attributes in the database and raise an error if validation failed.*
+     -
+        .. code-block:: ruby
+
+          person.update_attributes!(
+            first_name: "Leo",
+            last_name: "Tolstoy"
+          )
+
    * - ``Model#update_attribute``
 
        *Update a single attribute, bypassing validations.*
@@ -440,4 +452,4 @@ To create a collection with a default collation from the Mongo console:
 
 .. code-block:: javascript
 
-  db.createCollection("name", { collation: { locale: 'fr' } });
+  db.createCollection("name", { collation: { locale: 'fr' } });