chore(contrib): bump coreos to v349.0.0

```
core@deis-1 ~ $ docker version
Client version: 1.0.0
Client API version: 1.12
Go version (client): go1.2
Git commit (client): 63fe64c
Server version: 1.0.0
Server API version: 1.12
Go version (server): go1.2
Git commit (server): 63fe64c
core@deis-1 ~ $ fleetctl --version
fleetctl version 0.4.0
core@deis-1 ~ $ etcdctl --version
etcdctl version 0.4.3
```
Yes, I built the builder from scratch and it seemed fine for me, though it could've somehow used the cached layer (but doubt it due to #904). I'll re-verify