pylint configuration is not documented

[prakashsurya]

Currently we use some -d flags to pylint to disable some of its checks, but we don't have our motivation documented to explain why we're using those flags. We should find a good way to document why we're using the flags that we're using, perhaps by converting to a .pylintrc file with the relevant commentary.

[sdimitro]

That's a great idea!

Mentioning comment from recent PR that raised an issue regarding this: https://github.com/delphix/sdb/pull/76#discussion_r348068508