Improve compatibility of ColoredFormatter initializer arguments (#64, #75)

This is backwards incompatible with callers using positional arguments to call ColoredFormatter.__init__() however it improves compatibility with the Python standard library.

Author: xolox

coloredlogs/__init__.py

@@ -992,7 +992,7 @@ class ColoredFormatter(BasicFormatter):
  when you call :func:`coloredlogs.install()`.
  """
 
- def __init__(self, fmt=None, datefmt=None, level_styles=None, field_styles=None, style=DEFAULT_FORMAT_STYLE):
+ def __init__(self, fmt=None, datefmt=None, style=DEFAULT_FORMAT_STYLE, level_styles=None, field_styles=None):
  """
  Initialize a :class:`ColoredFormatter` object.