Rough draft of modules

This includes a naive implementation of a module system where imported
files have their imports recursively handled, strips the module/import
AST nodes, and then evals everything into a flat environment using
namespace prefixes like "Module.function".

src/REPL.hs

@@ -26,7 +26,7 @@ repl env = runInputT defaultSettings (loop env)
         | Just s  <- minput, strip s == ""      -> do
           outputStrLn ""
           loop env
-        | Just s  <- minput, strip s == "!load" -> do
+        | Just s  <- minput, strip s == "!import" -> do
           path <- getInputLine "File path to load < "
           if
             | Nothing <- path -> do