Add example of version specific pkg.install in the pillar

As far as I understand it, the `pkg:wanted` pillar key is fed directly to `pkg.installed: pkgs` so one can use that to have version specific specs : 

```
    wanted:
      - git
      - less
      - bc
      - curl
      - fail2ban
```

replaced by 

```
    wanted:
      - git
      - less
      - bc
      - curl
      - fail2ban: 0.10.2-2.1
``` 