Add "SimpleT" t output form

This new output form allows easy piping to the decode function of the
tricu executable. Includes a new test for roundtrip evaluation of map,
compilation to tree calculus terms, and decoding back to a human
readable string.

tricu.cabal

@@ -17,15 +17,8 @@ executable tricu
   hs-source-dirs:
       src
   default-extensions:
-      ConstraintKinds
-      DataKinds
       DeriveDataTypeable
-      DeriveGeneric
-      FlexibleContexts
-      FlexibleInstances
-      GeneralizedNewtypeDeriving
       OverloadedStrings
-      ScopedTypeVariables
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -optl-pthread -fPIC
   build-depends:
     base >=4.7
@@ -34,6 +27,7 @@ executable tricu
     , haskeline
     , megaparsec
     , mtl
+    , text
   other-modules:
     Compiler
     Eval
@@ -48,6 +42,9 @@ test-suite tricu-tests
   type:                exitcode-stdio-1.0
   main-is:             Spec.hs
   hs-source-dirs:      test, src
+  default-extensions:
+      DeriveDataTypeable
+      OverloadedStrings
   build-depends:       
     base
     , cmdargs
@@ -58,6 +55,7 @@ test-suite tricu-tests
     , tasty
     , tasty-hunit
     , tasty-quickcheck
+    , text
   default-language:    Haskell2010
   other-modules:
     Compiler