Add back logging (working this time)

Remove custom log formatter and make logging inheritable. By "inheritable" I
mean setting Quickeebooks.logger.level will affect the level of
Quickeebooks::Online::Service::ServiceBase.logger and
Quickeebooks::Windows::Service::ServiceBase.logger (unless those loggers have
been overwritten).
Merge pull request #4 from FundingGates/ew-fix-harvest-logging

Logging-related fixes/updates