Linting merge refactor

Hi.

This is a full refactor of the linting merge branch mainly to fix PEP-8 violations and some really weird code that I guess comes inherit from SublimeLinter.

Good work to @NorthIsUp and @JulianEberius with this "port" because it's more flexible than the original SublimeLinter project, now we don't have Python3 linting in Python2 files and that's really great.

Regards.