fix(cmd): create unit file templates as readable to all users

This change makes our recommended install `curl -sSL http://deis.io/deisctl/install.sh | sudo sh` work correctly for non-root users by ensuring that */var/lib/deis/units* and its unit file templates are readable.

Without this fix, the workaround is to run `deisctl` with `sudo`, or to install the unit file templates to the local search directory:
```console
$ deisctl refresh-units -p ~/.deis/units
```

Fixes #59.