Clean up linting

We have a lot of minor violations/"warnings", some of them for rules I'm not sure we actually care about using. Similarly, there are some swiftlint rules that might be useful to us but are not enabled by default.

We should decide what rules we want to disable / opt in to, and then fix all violations in the codebase.

We should also considering adding "swiftlint autocorrect" to "make".

We should have travis test this