increase poolSize to 10 from default 5

src/database/mongo.js

@@ -55,8 +55,13 @@
 			winston.error('Unable to initialize MongoDB! Is MongoDB installed? Error :' + err.message);
 			process.exit();
 		}
-
-		mongoClient.connect('mongodb://'+ nconf.get('mongo:host') + ':' + nconf.get('mongo:port') + '/' + nconf.get('mongo:database'), function(err, _db) {
+		var connString = 'mongodb://'+ nconf.get('mongo:host') + ':' + nconf.get('mongo:port') + '/' + nconf.get('mongo:database');
+		var connOptions = {
+			server: {
+				poolSize: 10
+			}
+		};
+		mongoClient.connect(connString, connOptions, function(err, _db) {
 			if(err) {
 				winston.error("NodeBB could not connect to your Mongo database. Mongo returned the following error: " + err.message);
 				process.exit();