Add Healthchecks (https://healthchecks.io)

README.md

@@ -372,6 +372,7 @@
   * [check_mk](http://mathias-kettner.com/check_mk.html) - Collection of extensions for Nagios.
   * [Dash](https://github.com/afaqurk/linux-dash) - A low-overhead monitoring web dashboard for a GNU/Linux machine.
   * [Flapjack](http://flapjack.io/) - Monitoring notification routing & event processing system.
+  * [Healthchecks](https://healthchecks.io/) - Monitoring for cron jobs, background services and scheduled tasks.
   * [Icinga](https://www.icinga.org/) - Nagios fork that has since lapped nagios several times. Comes with the possibility of clustered monitoring - ([Source Code](https://github.com/Icinga)) - `GPLv2`
   * [LibreNMS](http://www.librenms.org) - Fully featured network monitoring system that provides a wealth of features and device support.
   * [Monit](http://mmonit.com/monit/#home) - Small utility for managing and monitoring Unix systems.