Added a `userLeave` hook that gets called when a user leaves a pad

doc/api/hooks_server-side.md

@@ -263,3 +263,20 @@ exports.exportFileName = function(hook, padId, callback){
   callback("newFileName"+padId);
 }
 ```
+
+## userLeave
+Called from src/node/handler/PadMessageHandler.js
+
+This in context:
+
+1. session (including the pad id and author id)
+
+This hook gets called when an author leaves a pad. This is useful if you want to perform certain actions after a pad has been edited
+
+Example:
+
+```
+exports.userLeave = function(hook, session, callback) {
+  console.log('%s left pad %s', session.author, session.padId);
+};
+```

src/node/handler/PadMessageHandler.js

@@ -145,6 +145,9 @@ exports.handleDisconnect = function(client)
 
       //Go trough all user that are still on the pad, and send them the USER_LEAVE message
       client.broadcast.to(session.padId).json.send(messageToTheOtherUsers);
+
+      // Allow plugins to hook into users leaving the pad
+      hooks.callAll("userLeave", session);
     });
   }