Update CHANGELOG - v0.15.0
Update CHANGELOG - v0.15.0

Signed-off-by: Joffrey F <2e95f49799afcec0080c0aeb8813776d949e0768@docker.com>

docker/machine,dweomer/docker-machine,dweomer/docker-machine,exoscale/docker-machine,exoscale/docker-machine,docker/machine