Add unit test for ProfTransformer and ProfFilter

Hi,
I've added unit test for ProfTransformer and ProfFilter. And some code changes are made to make the code testable.
Could you please pull this changes?

BTW: found that DailyRollingFileWriter is coupled with MethodCache, and it's hard to make unit test without 'Manager.METHOD_LOG_PATH = "test.log"'. Could we use Log4J instead?