README: info about Ubuntu image and cleanup
README: info about Ubuntu image and cleanup

codedellemc/vagrant,austinpapp/playa-mesos,mesosphere/playa-mesos,codedellemc/vagrant,kaysoky/playa-mesos,emccode/vagrant,ilackarms/funC,ashayh/playa-mesos-centos,mesosphere/playa-mesos,agilemobiledev/playa-mesos,emccode/vagrant,ashayh/playa-mesos-centos,emccode/vagrant,austinpapp/playa-mesos,fpgeek/playa-mesos,codedellemc/vagrant,ilackarms/funC,project-emrys/development-environment,project-emrys/development-environment,kaysoky/playa-mesos,agilemobiledev/playa-mesos,fpgeek/playa-mesos