utf-8 and json dump log

a utf-8 and json dump log making easy conversation with third-party utility.

before this PR

```
2014-09-08 09:36:59,186 - [1] CryptoTransportLayer -                                  INFO - ON MESSAGE {u'pubkey': u'0401b6b9059fb6771728ee649d32f2cf1a92710ce971bc3d5a5c6c27306ee6bb09df2a6c2ce07eed4482da76b4ae2f0fb678b1ddbf7045a976556d9f92f9c697b6', u'senderGUID': u'04b11b8725662b0b734e6b622dfd91002188fdc9', u'senderNick': u"Sagan's Emporium", u'uri': u'tcp://49.143.231.159:12345', u'type': u'hello'}
```
![before-utf8](https://cloud.githubusercontent.com/assets/1840874/4183836/e14d460e-3741-11e4-9e9f-70444dd0f277.jpg)

after this PR

```
2014-09-08 10:15:11,709 - [1] CryptoTransportLayer - INFO - ON MESSAGE {"pubkey": "046a8988427dd298bee0792c8b5d02debe26b66d5975049dc1695b8c4b24ceffd14d6b256541a2144dbf1ac3ebf3b6ebc884cefdb15d06cf61ae44647f5890bb6d", "senderGUID": "38f2294d84c192e606b234739b5004297ccebf76", "senderNick": "seed.openlabs.co", "uri": "tcp://104.131.22.22:12345", "type": "hello"}
```

![after-utf8](https://cloud.githubusercontent.com/assets/1840874/4183838/e9a88e94-3741-11e4-9f00-098a9ec1b2ea.jpg)