added a new check for miss ratio
added a new check for miss ratio

Elbandi/nagios-plugin-mongodb,alexp789/nagios-plugin-mongodb,mzupan/nagios-plugin-mongodb,a-yiorgos/nagios-plugin-mongodb,MingjunZhao/Mapscape-Nagios-Mongo,hdeheer/nagios-plugin-mongodb,adrianlzt/nagios-plugin-mongodb,cookbooks/nd-nagios-plugin-mongodb,warrenpnz/nagios-plugin-mongodb