Better Backends

[kztk-m]

Original report by Kazutaka Matsuda (Bitbucket: kztk, GitHub: kztk-m).

---

The current implementation handles input programs as:

Surface ASTs --> Renamed Asts --> Typed Asts --> Desugared Asts --> Haskell-like Representations --> Template Haskell 
                                                       | 
                                                       v
                                                      REPL 

REPL should be performed for the representations in the one-step later phase.