lint the entire python client code base

PEP 8: https://github.com/Sage-Bionetworks/synapsePythonClient/pull/559

More PEP 8: https://github.com/Sage-Bionetworks/synapsePythonClient/pull/560/files

Another clean up: https://github.com/Sage-Bionetworks/synapsePythonClient/pull/561

, I have lint the code base to my satisfaction at the moment. Anything that could be clean up without refactor work, I have done so. The rest, I documented the warnings that will not be resolved in the scope of this ticket. More refactor work is required before we can clean up all warnings. And for some warnings, we won't be able to get rid of them until we stop supporting Python 2.

I would like you to validate that the code base is cleaned up to your satisfaction. If not, please reopen the ticket. Please keep in mind that this will be moved to future release if it's reopen.

looks good!