Goal Zero: Proprety based testing applied to code snippets

[timothycrosley]

This ticket is part of an aspirational goal for the isort project to achieve zero regressions through the remaining life of the 5.0.0 release, without slowing down the release velocity.

isort should utilize hypothesis to autogenerate a large number of configuration combinations and apply them to a complex code that contains imports, comments, and unrelated code. And ensure that no comments are removed and everything that should remain does, independent to the configuration combinations utilized.