- Cache the translations from severity to level and string in dicts,
  so these are normally done with a single dict.get() call rather than
  a Python function call.

- Extract the PEP 282 level first, and check it against the effective
  level of the logger, so we can take an early exit if the logger
  won't handle the event.

- Got rid of textwrap.  It slows things down, can frustrate grepping
  programs, and wasn't effective unless you were using Python 2.3
  anyway.

- Got rid of the addHandler(NullHandler()) (seems like superstition).

- Got rid of the log_format class variable (YAGNI).