[MIG] Upgrade version from 8 -> 9

mail_optional_follower_notification/README.rst

@@ -25,7 +25,7 @@ This field it's initialized to true to keep the standard behavior.
 
 .. image:: https://odoo-community.org/website/image/ir.attachment/5784_f2813bd/datas
    :alt: Try me on Runbot
-   :target: https://runbot.odoo-community.org/runbot/205/8.0
+   :target: https://runbot.odoo-community.org/runbot/205/9.0
 
  * https://www.odoo.com/forum/help-1
 
@@ -45,6 +45,7 @@ Contributors
 ------------
 
 * Adrien Peiffer <adrien.peiffer@acsone.eu>
+* Laurent Mignon <laurent.mignon@acsone.eu>
 
 Maintainer
 ----------

mail_optional_follower_notification/__openerp__.py

@@ -11,7 +11,7 @@
               'Odoo Community Association (OCA)',
     'website': "http://acsone.eu",
     'category': 'Social Network',
-    'version': '8.0.1.0.0',
+    'version': '9.0.1.0.0',
     'license': 'AGPL-3',
     'depends': [
         'mail',