Update documentation

docs/notifications.markdown

@@ -0,0 +1,30 @@
+Notifications
+=============
+
+Kanboard is able to send notifications through several channels:
+
+- Email
+- Jabber/XMPP
+- Hipchat
+- Slack
+
+Actually, Jabber/Hipchat/Slack notifications are sent to a room or group channel because they are configured at the project level.
+However, email notifications are sent to an individual.
+
+User notifications
+------------------
+
+Each user must enable the notifications in their profile: **User Profile > Email notifications**. It's disabled by default.
+
+You need of course a valid email address in you profile and the application must be configured to send emails.
+
+![Notifications](http://kanboard.net/screenshots/documentation/notifications.png)
+
+For each project your are member, you can choose to receive notifications for:
+
+- All tasks
+- Only for tasks assigned to you
+- Only for tasks created by you
+- Only for tasks created by you and assigned to you
+
+You can also select only some projects, by default it's all projects where you are member.