Feature/api versioning (#106)

* wip

* finishes initial refactor

* prune unused code

* finished massive refactor

* remove commented deps

* fix import

* fix bug

fourmolu.yaml

@@ -0,0 +1,8 @@
+indentation: 4
+comma-style: leading
+record-brace-space: false
+indent-wheres: true
+diff-friendly-import-export: true
+respectful: true
+haddock-style: single-line
+newlines-between-decls: 2