Add PreCommit::PreventDebugger

Closes #7
Although I agree that debugging log is sometimes pretty valuable in production code, I think the main intent here is not to allow someone to inadvertently commit the `logger.debug` line. You can always issue your commit with the `--no-verify` flag if your intent is to bypass the verification.

I think the main point that needs to be understood is the following: Most of the times we add a `logger.debug` to the code, do we intent it to become production code? In my experience, that is not the case, hence, I think the validation should be there.