Clean up and fix compilation error

app/Main.hs

@@ -1,6 +1,4 @@
 module Main where
 
-import Rextra.Rextra (rextra)
-
 main :: IO ()
-main = rextra
+main = putStrLn "Nothing to see here"

src/Rextra/Automaton.hs

@@ -153,7 +153,7 @@ initialPartition a =
 minimizeDfa :: (Ord s, Ord t) => Dfa.Dfa s t -> Dfa.Dfa (EquivalenceGroup s) t
 minimizeDfa a =
   let grouping      = findGroupingFixpoint (stateMap a) (initialPartition a)
-      mapping       = partitionToMap $ groupingToPartition grouping
+      mapping       = partitionToMap $ Map.keysSet grouping
       newEntryState = mapping Map.! entryState a
       newExitStates = Set.map (mapping Map.!) (exitStates a)
   in  fromJust $ fa grouping newEntryState newExitStates

src/Rextra/Rextra.hs

@@ -1,6 +0,0 @@
--- This file will be split up as it grows.
-module Rextra.Rextra where
-
--- * Just a placeholder function
-rextra :: IO ()
-rextra = putStrLn "rextra"