reflect change in github url (#496)

CONTRIBUTING.md

README.md

build-ci.sh

cmd/main.go

delivery.yaml

docs/developer.md

docs/gsoc-2019/ideas.md

docs/index.md

docs/quickstart.md

docs/reference/cluster_manifest.md

docs/reference/operator_parameters.md

docs/user.md

glide.yaml

hack/update-codegen.sh

mkdocs.yml

pkg/apis/acid.zalan.do/v1/crds.go

pkg/apis/acid.zalan.do/v1/operator_configuration_type.go

pkg/apis/acid.zalan.do/v1/register.go

pkg/apiserver/apiserver.go

pkg/cluster/cluster.go