Expose supervision information in json

sponges now provides a http server to expose information about pool's
health. By default, this server listen on port 5032. The port can be
configured with the `port` accessor on `config`.

This may be used for monitoring, and building tools like dashboard.

Response:

    {
      "supervisor":{
        "pid":11537,
        "pctcpu":0.0,
        "pctmem":0.22,
        "created_at":"2013-03-05 15:21:04 +0100"
      },
      "children":[
        {
          "pid":11540,
          "pctcpu":0.0,
          "pctmem":0.21,
          "created_at":"2013-03-05 15:21:04 +0100"
        },
        {
          "pid":11543,
          "pctcpu":0.0,
          "pctmem":0.21,
          "created_at":"2013-03-05 15:21:04 +0100"
        },
        {
          "pid":11546,
          "pctcpu":0.0,
          "pctmem":0.21,
          "created_at":"2013-03-05 15:21:04 +0100"
        },
        {
          "pid":11549,
          "pctcpu":0.0,
          "pctmem":0.21,
          "created_at":"2013-03-05 15:21:04 +0100"
        }
      ]
    }

Signed-off-by: chatgris <jboyer@af83.com>
Bump version

Signed-off-by: chatgris <jboyer@af83.com>
README and CHANGELOG

Signed-off-by: chatgris <jboyer@af83.com>