Upgrade Dockerfile to use latest stable Alpine which has Go 1.6
Upgrade Dockerfile to use latest stable Alpine which has Go 1.6

Fitbit/confd,rancher/confd,rancher/confd,bacongobbler/confd,okushchenko/confd,okushchenko/confd,kelseyhightower/confd,blippar/confd,bacongobbler/confd,blippar/confd,kelseyhightower/confd,Fitbit/confd