make log rotation configurable
fix import
midnight should be a string
adding test file for logger
improve tests

Test various aspects of the logger module.
add docstrings to the unit-tests
update comment
check that deactivation of log file rotation works
fixup NullHandler for python2.6
move the test_logger to tests to comply with the travis setup
try fixing error reported by travis
add missing temp_dir
try fixing the log dir via the test settings
fixup the info test