new release: add grok extension

[rchicoli]

add grok feature

[rchicoli]

this looks cool:

{
  "took": 7,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 1,
    "max_score": 1,
    "hits": [
      {
        "_index": "docker",
        "_type": "log",
        "_id": "AWIHV72s5dJofV9tBo-V",
        "_score": 1,
        "_source": {
          "containerID": "5ad82a912d4a",
          "containerName": "webapper",
          "containerImageName": "rchicoli/webapper",
          "containerCreated": "2018-03-08T20:40:11.997781535Z",
          "source": "stdout",
          "timestamp": "2018-03-08T20:40:13.162255674Z",
          "partial": false,
          "grok": {
            "auth": "-",
            "bytes": "207",
            "clientip": "127.0.0.1",
            "httpversion": "1.1",
            "ident": "-",
            "rawrequest": "",
            "request": "/index.php",
            "response": "404",
            "timestamp": "23/Apr/2014:22:58:32 +0200",
            "verb": "GET"
          }
        }
      }
    ]
  }
}

[rchicoli]

TODO before releasing:

• update readme
• add warning note for docker version 17.09
• add grok-pattern, grok-pattern-file and grok-pattern-path

  When you want to add a custom pattern, use the grok.AddPattern(nameOfPattern, pattern), see the example folder for an example of usage. You also can load your custom patterns from a file (or folder) using grok.AddPatternsFromPath(path), or PatterndDir configuration.