new module: resolver. Obtains nameserver entries from /etc/resolv.conf

Example:

```
ansible www -m resolver
www | success >> {
    "nameservers": [
        "172.16.153.1",
        "127.0.0.1",
        "192.168.1.1",
        "2001:1234:800:1d2e:aa20:33:2c:01"
    ]
}
```