some 0.14 love

Hi,

I made some changes to make ExKanren work with Elixir 0.14.x.

They fall into 4 categories and/or reasons:

- there's no more HashDict.new/1  ->  now using Enum.into
- in new Elixir impl, HashDict seems to have random order of keys, invalidating equalities in tests -> switched to Map
- state dict uses now functions from Dict module - in order to switch easily between HashDict and Map
- some eof LFs which annoned my git.

Enjoy and thanks for this piece of code!