Add container health metrics to docker input (#3666)

plugins/inputs/docker/README.md

@@ -199,6 +199,9 @@ based on the availability of per-cpu stats on your system.
     - network
 - docker_container_blkio specific:
     - device
+- docker_container_health specific:
+    - health_status
+    - failing_streak
 - docker_swarm specific:
     - service_id
     - service_name
@@ -257,4 +260,4 @@ io_serviced_recursive_total=6599i,io_serviced_recursive_write=107i 1453409536840
 >docker_swarm,
 service_id=xaup2o9krw36j2dy1mjx1arjw,service_mode=replicated,service_name=test,\
 tasks_desired=3,tasks_running=3 1508968160000000000
-```
+```