Respect configuration of specific logger when redirecting to std logging

[hongquan]

Scenario:

• My project is Django-based. I have 2 place to to consume logs: console and a cloud service.
• I want log messages generated by a module to go to cloud service, not to console, so I configure a dict like this, in Django settings (LOGGING):

{
    'root': {
        'handlers': ['console', 'cloud']
    },
    'loggers': {
        'device': {
            'handlers': ['cloud']
        }
    }
}

• Then I use logbook.compat.LoggingHandler to redirect my messages to standard logging.

The issue is that, all messages from device goes to console also. This PR is to fix that.

[coveralls]

Coverage increased (+0.03%) to 76.881% when pulling 53dc356 on hongquan:bugfix/respect_specific into 185b9ed on getlogbook:develop.