feat(scheduling): simple method of running a unit file
feat(scheduling): simple method of running a unit file

* Poll the /coreos.com/coreinit/schedule/ namespace in etcd for systemd unit files
* When a new unit file appears, write it out to the local filesystem and
  remove the key from etcd

improbable-io/fleet,WPMedia/fleet,dongsupark/fleet,dalbani/fleet,giantswarm/fleet,ecnahc515/fleet,jonboulle/fleet,coreos/fleet,dalbani/fleet,endocode/fleet,bviswana101/fleet,mwhooker/fleet,mwitkow/fleet,mwitkow-io/fleet,improbable-io/fleet,bcwaldon/fleet,jonboulle/fleet,mookjp/fleet,hhoover/fleet,WPMedia/fleet,dongsupark/fleet,webwlsong/fleet,ecnahc515/fleet,paveltiunov/fleet,octoblu/fleet,paveltiunov/fleet,bviswana101/fleet,giantswarm/fleet,mwhooker/fleet,thepwagner/fleet,mwitkow-io/fleet,mookjp/fleet,wuqixuan/fleet,flandr/fleet,thepwagner/fleet,bcwaldon/fleet,dalbani/fleet,dongsupark/fleet,improbable-io/fleet,coreos/fleet,esatterwhite/fleet,mwitkow/fleet,coreos/fleet,jonboulle/fleet,mischief/fleet,wuqixuan/fleet,octoblu/fleet,webwlsong/fleet,endocode/fleet,mischief/fleet,esatterwhite/fleet,endocode/fleet,ecnahc515/fleet,hhoover/fleet,giantswarm/fleet,bcwaldon/fleet,flandr/fleet