Allow to specify an instance name per logger

The instance field can be set to extend the logger name with the string
'.__INSTANCE__', e.g. to specify the special purpose of a class in the
logger hierarchy for better controlled logging configuration.

* loggerbyclass.py: add instance parameter to get_logger_by_class
* setup.py: version bump to 0.2

loggerbyclass.py

@@ -29,12 +29,14 @@
 import logging
 
 
-def get_logger_by_class(klass):
+def get_logger_by_class(klass, instance=None):
     """Gets a python logger instance based on a class instance. The logger name
     will be a dotted string containing python module and class name, hence
     being the full path to the class.
 
     @param klass: class instance
     @return: logger instance
     """
-    return logging.getLogger(klass.__module__ + "." + klass.__name__)
+    return logging.getLogger(klass.__module__ + "." + klass.__name__ +
+                             (".__{}__".format(instance.replace('.', '_'))
+                              if instance else ""))

setup.py

@@ -21,7 +21,7 @@
 from setuptools import setup, find_packages
 
 setup(name='loggerbyclass',
-      version='0.1.0',
+      version='0.2.0',
       description='''
                   Provides a single helper function to simplify the common idiom
                   of getting one logger object from python standard logging per