Add Vagrant for easier usage on OS X

Use boot2docker as a small VM to run docker inside:
 - Use dduportal's variant as it supports VirtualBox shared folders
 -  Setup /Users:/Users as a synced folder so one can use the docker
    --volume option from OS X easily. That is, as long as the directory
    to mount into the docker container is below /Users
 - Fix location of docker binary so Vagrant doesn't try to install it
 - Fix DNS problems by restarting dhcpc and docker when provisioning