Update to latest cAdvisor version and add a client package for cAdvisor

This PR updates kubelet's code to use the most recent cAdvisor's API.

The current problem I encountered here is where should I put the data structures' definition.

There are several data structures' in cAdvisor describing CPU/Memory stats/specs. To retrieve stats from cAdvisor through kubelet, we could either use cAdvisor's data structures, or redefine (almost) the same structures in k8s' api package.

If we reuse cAdvisor's data structure, then there will be less copy&paste work. However, we will force kubelet users (i.e. the master) to import one of cAdvisor's package (``github.com/google/cadvisor/info``).

If we redefine all, or some data structures in api, then there'll be lots of boilerplate copied from cadvisor.

Currently, I'm using the second approach (copy all data structures in the api package.) But I'm open to change. So please feel free to add any comment here.