Add folsom-stats

folsom-stats will remote into a running erchef instance and gather the folsom
metrics, dumping them to a json array. Only runs with chef-server 12.
we should probably use _safe_get in this. not calling error! on mixlib covers many potential failures but not all. the idea in this script is to grab anythign we can and if we encounter a failure, just keep trying other stuff, not ever fail completely. if something is missing you should catch it because of the resulting missing data in your resulting dataset