Run flake8 and tidy up code

[pbugnion]

Many of the older parts of sml-sync remain embarrassingly untidy. This is a particularly bad because it makes it harder to enforce best practices for new contributions.

We should run flake8 and tidy up anything that comes up.

[srstevenson]

I'm happy to take this on.

[pbugnion]

Thank you! I think that, if we do this, we should add a Travis flake8 check (otherwise we'll just regress).

[srstevenson]

Agreed!