Add docker support for running executor

[qianglchina]

Hi,
We are running our business all by virtual network in docker, right now mesos slave starts executor just by command, can it be run by docker container?

[LLParse]

+1

[liorze]

+1. Is there a particular reason that it does not run in a docker container? @joestein, maybe you could help here.

[krishnabigdata]

+1, Please let us know when this docker support will be provided, is there any specific reason, this is not provided?

[steveniemitz]

I've opened #270 as a catch-all for docker support, closing this one.