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",
        "2001:808:910:1321:aa20:66ff:e2c:123"
    ],
    "searchlist": [
        "example.com",
        "example.org",
        "sub.example.org"
    ]
}
```