draft post on Docker

Hey team,

Added a draft post on Docker.  Would appreciate any comments/edits/suggestions.  Please merge when you feel it's ready to go (adjusting the date as appropriate, I just threw tomorrow's date on as a placeholder).  
@cboettig  I wonder if you should mention whether or not the docker code base is open source or not?  If it is, then that I think would allay anyone's fear that the technology could go away if they fold