fix grok match pattern


fix grok match pattern to make log contract easier to search.

log message 

```
2014-09-09 02:23:59,338 - [1] CryptoTransportLayer - INFO - ON MESSAGE {"senderGUID": "87d8d3420c83596799daabc94cbf655183b8b7d3", "senderNick": "OpenBazaar Polo Shirts", "deleted": 0, "type": "listing_result", "uri": "tcp://162.247.54.200:12345", "unit_price": "0.04", "item_quantity_available": 1, "item_title": "6 of 12: OpenBazaar Polo Shirt - Large", "item_desc": "Please read the details carefully. This is a real sale, it is NOT a test. ///\n\nYou are participating in a group buy for 1 Large white polo shirt with the OpenBazaar logo on the breast. See the picture for the logo that was chosen - it includes the name OpenBazaar as well as the github logo. In order for the sale to complete, 12 shirts must be sold before Sunday, September 28, 2014 @ midnight EST. ///\n\nYou may be at some risk of losing funds if there is a problem with the OpenBazaar marketplace. If the sale does not complete, you should be able to receive a full refund, though this functionality is untested. ///\n\nIf the sale completes, I will submit an order for 12 large polo shirts and mail your shirt to you. ///\nThe cost is 0.04 for the shirt and 0.025 for shipping. I worked to provide the most accurate estimate possible. If the estimate is under, I will cover the difference; if the estimate is high I will keep the difference. ///\n\nPlease feel free to contact me with questions at balnix2@gmail.com or through bitmessage at BM-NB8cyH3NHm8ybPUAoyAfdNmxVJRrLLVo ///\nSee the shirt here: http://i.imgur.com/K5MNP8t.png";, "signed_contract_body": "-----BEGIN PGP SIGNED MESSAGE--..."}
```

After this PR from Kinaba dashboard.

```
$ git clone https://github.com/OpenBazaar/OpenBazaar && cd OpenBazaar
$ cd test/docker/logelk
$ bash build.sh -a
$ sudo fig up -d
$ sudo fig logs
```

OB node http://DOCKER_HOST:8888/

ElasticSearch/Logstash/Kibana http://DOCKER_HOST:9280/
![after-log-contract2](https://cloud.githubusercontent.com/assets/1840874/4198287/333d607e-37f7-11e4-851d-0ce2902f8c07.jpg)