The doc about Package Generator is out-of-date

[cang233]

I find the doc in https://github.com/intel-go/nff-go/blob/master/examples/nffPktgen/README.md is out-of-date. I found that the "incr" and "ip" key is no used. Here is the runnable json I modified:

{
    "mix1": {
        "ether": {
            "saddr": {
                "range": {
                    "min": "00:25:96:FF:FE:12",
                    "start": "00:30:00:FF:FE:12",
                    "max": "00:FF:96:FF:FE:12"
                }
            },
            "daddr": "00:FF:96:FF:FE:12",
            "randbytes": {
                "size": 40,
                "deviation": 0
            }
        },
        "quantity": 6
    },
    "mix2": {
        "ether": {
            "saddr": "00:FF:96:FF:FE:12",
            "daddr": "00:FF:96:FF:FE:12",
            "randbytes": {
                "size": 500,
                "deviation": 0
            }
        },
        "quantity": 3
    },
    "mix3": {
        "ether": {
            "saddr": "00:25:96:FF:FE:12",
            "daddr": "00:00:96:FF:00:00",
            "ipv4": {
                "saddr": "1.1.127.1",
                "daddr": "1.1.1.3",
                "tcp": {
                    "sport": 8080,
                    "dport": 2000,
                    "seq": "increasing",
                    "flags": ["ack", "fin", "syn"],
                    "randbytes": {
                        "size": 1466,
                        "deviation": 0
                    }
                }
            }
        },
        "quantity": 1
    }
}