Add listeners for end, error and ready on Redis sessions

Also add support for `onDisconnect()` and `onReconnect()` in session config

lib/hooks/session/ensure-redis-connection.js

@@ -2,7 +2,7 @@
  * Module dependencies.
  */
 var flaverr = require('flaverr');
-
+var _ = require('@sailshq/lodash');
 
 /**
  * ensureRedisConnection()
@@ -72,6 +72,19 @@ module.exports = function ensureRedisConnection(app, cb) {
   client.once('ready', function onConnectionReady(){
     client.removeListener('end', onPreConnectionEnd);
     client.removeListener('error', onPreConnectionError);
+    client.on('end', function(){
+      if (_.isFunction(app.config.session.onDisconnect)) {
+        app.config.session.onDisconnect();
+      }
+      app.log.error('Redis session server went off-line...');
+    });
+    client.on('error', function(err){app.log.verbose('Redis session server reported error: ', err.stack);});
+    client.on('ready', function(err){
+      if (_.isFunction(app.config.session.onReconnect)) {
+        app.config.session.onReconnect();
+      }
+      app.log.error('Redis session server came back on-line...');
+    });
     return cb();
   });