update sensu homepage, description, add source code link

- ref. https://github.com/awesome-foss/awesome-sysadmin/issues/416

README.md

@@ -527,7 +527,7 @@ _See also: [IT Asset Management]([Ralph](#it-asset-management))_
 - [Riemann](http://riemann.io/) - Flexible and fast events processor allowing complex events/metrics analysis. ([Source Code](https://github.com/riemann/riemann))
 - [rtop](https://github.com/rapidloop/rtop) - an interactive, remote system monitoring tool based on SSH. ([Source Code](https://github.com/rapidloop/rtop))
 - [Scrutiny](https://github.com/AnalogJ/scrutiny) - Hard Drive S.M.A.R.T Monitoring, Historical Trends & Real World Failure Thresholds 
-- [Sensu](https://sensuapp.org/) - Monitoring framework.
+- [Sensu](https://sensu.io/) - Monitoring tool for ephemeral infrastructure and distributed applications. ([Source Code](https://github.com/sensu/sensu-go))
 - [ServerStatus BotoX](https://github.com/BotoX/ServerStatus) - Display and monitor your servers statistics in a beatiful way.
 - [ServerStatus moejda](https://github.com/mojeda/ServerStatus) - Server Status website script, displays uptime (days), free RAM, free HDD
 - [Thruk](http://www.thruk.org/) - Multibackend monitoring web interface with support for Naemon, Nagios, Icinga and Shinken.