Added SPM by Sematext to section 'advanced instrumentation' 

I added Sematext SPM to the advanced intrumentation section in the monitoring document. 

According to this: 
http://www.prnewswire.com/news-releases/sematext-announces-the-first-monitoring-alerting-and-anomaly-detection-solution-for-apache-spark-in-spm-278378361.html