telegraf: add license, language, update description

- ref. #416

README.md

@@ -543,7 +543,7 @@ _See also: [Databases](#databases)_
 - [RRDtool](https://oss.oetiker.ch/rrdtool/) - Industry standard, high performance data logging and graphing system for time series data. ([Source Code](https://github.com/oetiker/rrdtool-1.x)) `GPL-2.0` `C`
 - [Statsd](https://github.com/etsy/statsd/) - Daemon that listens for statistics like counters and timers, sent over UDP or TCP, and sends aggregates to one or more pluggable backend services. `Nodejs` `MIT`
 - [tcollector](http://opentsdb.net/docs/build/html/user_guide/utilities/tcollector.html) - Gathers data from local collectors and pushes the data to OpenTSDB. ([Source Code](https://github.com/OpenTSDB/tcollector/)) `LGPL-3.0/GPL-3.0` `Python`
-- [Telegraf](https://github.com/influxdata/telegraf) - The plugin-driven server agent for collecting & reporting metrics.
+- [Telegraf](https://github.com/influxdata/telegraf) - Plugin-driven server agent for collecting, processing, aggregating, and writing metrics. `MIT` `Go`
 
 
 ### Network Configuration Management