add node-bell to monitor

README.md

@@ -241,6 +241,7 @@ A curated list of amazingly awesome open source sysadmin resources inspired by [
 * [Munin](http://munin-monitoring.org/) - Networked resource monitoring tool.
 * [Naemon](http://www.naemon.org/) - Network monitoring tool based on the Nagios 4 core with performance enhancements and new features.
 * [Nagios](http://www.nagios.org/) - Computer system, network and infrastructure monitoring software application.
+* [Node-Bell](https://github.com/eleme/node-bell) - Real-time anomalies detection for periodic time series, metrics monitor.
 * [Observium](http://www.observium.org/) - SNMP monitoring for servers and networking devices. Runs on linux.
 * [OMD](http://omdistro.org/) - The Open Monitoring Distribution.
 * [Opsview](http://www.opsview.com/solutions/core) - Based on Nagios 4, Opsview Core is ideal for small IT and test environments.