+ system-metrics: fix #135 and includes the following new metrics:
** DiskMetrics
** NonHeapMetrics
** LoadAverageMetrics
** ThreadMetrics
** ClassLoadingMetrics
and closes #131
+ datadog: includes Disk, NonHeap LoadAverage, Threads and ClassLoading metrics
+ statsd: includes Disk, NonHeap LoadAverage, Threads and ClassLoading metrics