fix(contrib/gce): fix docker storage being wiped on boot

Ref: #1868
fix(controller): fix scale log event on git push
Merge pull request #1883 from Xe/fix/gce/no-more-nuking-data

fix(contrib/gce): fix docker storage being wiped on boot
docs(readme): cleanup readme after deisctl integration

docs(*): replace DockerHub with Docker Hub

doc(readme): change to approximately

docs(readme): replace sed with make discovery-url
docs(using_deis): add Using Docker Images section
Merge pull request #1887 from gabrtv/doc-updates

Update documentation in preparation for 0.12
Merge pull request #1886 from gabrtv/fix-scale-log

fix(controller): fix scale log event on git push
ref(builder): use ubuntu:14.04 as Dockerfile base image
ref(cache): use ubuntu:14.04 as Dockerfile base image
ref(controller): use ubuntu:14.04 as Dockerfile base image
ref(database): use ubuntu:14.04 as Dockerfile base image
ref(database): update postgres user uid/gid in confd templates
ref(logger): use ubuntu:14.04 as Dockerfile base image
ref(registry): use ubuntu:14.04 as Dockerfile base image
ref(router): use ubuntu:14.04 as Dockerfile base image
ref(tests): use ubuntu:14.04 as Dockerfile base image
chore(pip): update pip installs to 1.5.6
ref(data): use ubuntu:14.04 as Dockerfile base image