Update to latest AppVeyor configuration
Update to latest AppVeyor configuration

Previously, the build was failing with:

    the following programs are not installed properly:
     unzip
    I can't proceed :(

Signed-off-by: Thomas Leonard <ea62ade398c3addd3bcc52285a00e98f3b0c618f@docker.com>

docker/datakit,docker/datakit,docker/datakit