feat(store): add deis-store component

This is the deis-store component described in https://github.com/deis/deis/issues/1384.
It uses Ceph as a backing service, and features a blob store gateway that is
both Swift-compatible and S3-compatible.

Note that to test this, you will need Docker 1.2.0 and fleet 0.8.0+.

TESTING: build, install, and start the stores and the routers
```console
$ make -C store build
$ make -C router build
$ make install-routers install-stores start-routers start-stores
```

If you make changes and want to restart stores:
```console
$ make -C store stop build
$ make start-stores
```

After this, your cluster should look like the following:
```console
$ fleetctl --strict-host-key-checking=false list-units --fields unit,load,active,sub,machine
UNIT        LOAD  ACTIVE  SUB MACHINE
deis-router@1.service   loaded  active  running 442acc93.../172.17.8.102
deis-store-daemon@1.service loaded  active  running a852dd23.../172.17.8.100
deis-store-daemon@2.service loaded  active  running a3b47562.../172.17.8.101
deis-store-daemon@3.service loaded  active  running 442acc93.../172.17.8.102
deis-store-data@1.service loaded  active  exited  a852dd23.../172.17.8.100
deis-store-data@2.service loaded  active  exited  a3b47562.../172.17.8.101
deis-store-data@3.service loaded  active  exited  442acc93.../172.17.8.102
deis-store-gateway.service  loaded  active  running a3b47562.../172.17.8.101
deis-store-monitor@1.service  loaded  active  running a852dd23.../172.17.8.100
deis-store-monitor@2.service  loaded  active  running a3b47562.../172.17.8.101
deis-store-monitor@3.service  loaded  active  running 442acc93.../172.17.8.102
```

Once the services are running, you can enter one of the `deis-store-monitor` or `deis-store-daemon`
services and `ceph -s` to see the cluster health. To access the object store endpoint,
hit `http://store.local3.deisapp.com`. Your object store requests go through the router!

**To-Dos**
- [x] Write all monitor hosts to `ceph.conf` - right now we just list the initial monitor, but this means that if that monitor goes down, clients won't know how to access the cluster. We need to append to the conf file after the monitors are all up. See http://ceph.com/docs/firefly/dev/mon-bootstrap/#cluster-creation
- [x] Programmatically get the access key and secret key for the `deis` gateway user -- this key will be used by S3 and Swift clients to access the object store. Running `radosgw-admin user info --uid=deis` outputs the user info (including keys) as JSON, but we need to strip out the keys somehow
- [x] ~~Re-test the RDB volume mapping on CoreOS 431.0.0+, which includes kernel 3.16.1. On the 3.15.8 kernel I ran into [several](http://tracker.ceph.com/issues/8818) [issues](http://tracker.ceph.com/issues/9355).~~ Still can't map the RDB volume from within the container :(
- [ ] Test failure and disaster scenarios (stop a container and then start it later, etc.)
- [ ] Write integration tests for store
- [ ] Update docs anywhere we list the Deis components
- [ ] Configure automated builds in Docker Hub

replaces #1729