ref(store): reduce image size

```console
deis/store-gateway           git-adb3c37         b58aeb0e4bae        14 hours ago        365.9 MB
deis/store-daemon            git-adb3c37         7c91ac653be4        14 hours ago        310.3 MB
deis/store-monitor           git-adb3c37         33f2bcc45e02        14 hours ago        310.3 MB
deis/store-gateway           v0.13.1             f98554248def        5 days ago          472 MB
deis/store-daemon            v0.13.1             826ea6d38b40        5 days ago          419.1 MB
deis/store-monitor           v0.13.1             06dc7b4763fa        5 days ago          419.1 MB
```