__FILE__ is removed, use __DIR__ instead.

Though, I could have used __ENV__.dir per
https://github.com/elixir-lang/elixir/issues/1945
Fix order of result dict after upgrade to Elixir 0.12.3

This actually behaves more predictably now.
Enum.first was removed.
Fix usage instructions.
Use __DIR__ and List.first.
Fix filenames.
Use __DIR__.
Fix filename.
Order of items in set have changed, weird.
Use pattern matching to get private record field.

vec(record, field) is now deprecated