added cadvisor meter for host and services

[finishes: #80456090]

![screen shot 2014-10-14 at 2 11 22 pm](https://cloud.githubusercontent.com/assets/923211/4635062/f8d74fda-53d5-11e4-9ab1-6dd3650c2373.png)

Did you consider leaving the host_health_controller and adding a new service_health_controller? I guess it makes sense that these are separate calls, but I wonder if it would simplify implementation if it was just one api call?