Add a blocking get stats interface

[pmorton]

Hi - I am working on an application that consumes the dockerclient api! (woot) Specifically I am working with the stats API. The implementation of the stats API in this library and great and seems well suited for short lived client application. I am writing a daemon that will monitor the stats and have some additional requirements that don't seem to work well with the current implementation.

1. When an error occurs that causes the go routine to exit, I need to know the error and the container ID that it is related to.
2. I need to be able to ask a specific stats monitor (go routine) to stop politely
3. I would prefer to use channels over callbacks for `stat`` processing.

Thoughts?

[ehazlett]

Yeah I'm not sure either. When I added the original implementation I was thinking along the lines of the event stream which handles things that way (callback).

+1 for stopping events for a single container.

[donhcd]

@pmorton @ehazlett #71 handles the 3 requests that pmorton listed above - could you take a look at it? it has slightly more complex logic, but it's been tested and it works