Add collectors about network

In reference to Ohai, I added the following collector.

* ipaddress
* ipv6address
* macaddress
* network

The network collector collects information about the address of each interface, MTU, the flags.  
It is the output in the VM.

```json
{
    "network": {
        "interfaces": {
            "eth0": {
                "addresses": {
                    "08:00:27:60:fc:47": {
                        "family": "lladdr"
                    }, 
                    "10.0.2.15": {
                        "family": "inet"
                    }, 
                    "fe80::a00:27ff:fe60:fc47": {
                        "family": "inet6"
                    }
                }, 
                "flags": [
                    "UP", 
                    "BROADCASE", 
                    "MULTICAST"
                ], 
                "mtu": 1500
            }, 
            "lo": {
                "addresses": {
                    "127.0.0.1": {
                        "family": "inet"
                    }, 
                    "::1": {
                        "family": "inet6"
                    }
                }, 
                "flags": [
                    "UP", 
                    "LOOPBACK"
                ], 
                "mtu": 16436
            }
        }
    }
}
```