Updated README.md: Added OpenTSDB

Author: johann8384

README.md

@@ -223,6 +223,7 @@ A curated list of amazingly awesome open source sysadmin resources inspired by [
 * [Ganglia](http://ganglia.sourceforge.net/) - High performance, scalable RRD based monitoring for grids and/or clusters of servers. Compatible with Graphite using a single collection process.
 * [Graphite](http://graphite.readthedocs.org/en/latest/) - Open source scaleable graphing server.
 * [InfluxDB](http://influxdb.com/) - Open source distributed time series database with no external dependencies.
+* [OpenTSDB](http://opentsdb.net/) - OpenTSDB - Store and server massive amounts of time series data without losing granularity.
 * [RRDtool](http://oss.oetiker.ch/rrdtool/) - Open source industry standard, high performance data logging and graphing system for time series data.
 * [Statsd](https://github.com/etsy/statsd/) - Application statistic listener.