Public docker image live, updated docs

********* PEOPLE *************
Primary reviewer: @suntzu86 

Reviewers:

********* DESCRIPTION **************
Branch Name: sclark_332_set_up_public_docker
Ticket(s)/Issue(s): Closes #332 

********* TESTING DONE *************

Tested on dev and personal linux box
I want to explicitly have it in the install docs too. I don't think this is that big of a deal. I want it to be one of the first things people see on the homepage or if they blindly click/link install.