Be more mock friendly in MockDockerContainerizer.

Rather than having the MockDockerContainerizer store local variables
when certain events occur we can make the tests store what ever things
they need by mocking out the methods.
Display resources allocation in ResourceStatistics.
Support resources in docker run().
Refactored MockDockerContainerizer.
Fixed usage().

Check for destroying containers before calling docker.inspect().
Merge pull request #7 from yifan-gu/fix_usage

fix(usage)
Docker update