System IO refactor

[decioferreira]

The main change here revolved around the re-implementation of the IO monad, allowing for the removal of the need for the top level decoder.

As part of this work we had to move some of the data structures from modules like Compiler.Type.UnionFind, Compiler.Type.Type and Compiler.Elm.ModuleName into the IO monad modules, so that we can have them directly referred on the RealWorld record (before we had to use Decode.Value because otherwise we would create import cycles).

This also:

• seems to have solved fails to install ianmackenzie/elm-geometry package #33
• partially addresses split compiler/src/Utils.elm into multiple modules #10
• greatly improved performance (relates to review performance #37)

The improvement on performance was the following (from ~56:58.46 to ~2:28.32):

Before:

% time guida make --optimize --output=bin/guida.js src/Terminal/Main.elm 
Starting downloads...

  ● andre-dietrich/parser-combinators 4.1.0
  ● elm/time 1.0.0
  ● elm/json 1.1.3
  ● pilatch/flip 1.0.0
  ● elm/virtual-dom 1.0.3
  ● elm/regex 1.0.0
  ● elm/random 1.0.0
  ● elm/bytes 1.0.8
  ● fredcy/elm-parseint 2.0.1
  ● dasch/levenshtein 1.0.3
  ● rtfeldman/elm-hex 1.0.0
  ● elm/parser 1.1.0
  ● the-sett/elm-pretty-printer 3.1.0
  ● elm-community/basics-extra 4.1.0
  ● elm/url 1.0.0
  ● elm-community/array-extra 2.6.0
  ● elm-community/list-extra 8.7.0
  ● elm-community/maybe-extra 5.3.0
  ● obiloud/numeric-decimal 3.0.1
  ● elm/core 1.0.5
  ● zwilias/elm-rosetree 1.5.0
  ● guida-lang/graph 1.0.0
  ● guida-lang/glsl 1.0.0
  ● elm/html 1.0.0
  ● elm-explorations/test 2.2.0

Dependencies ready!           
Success! Compiled 132 modules.

    Terminal.Main ───> bin/guida.js

guida make --optimize --output=bin/guida.js src/Terminal/Main.elm  3666.89s user 249.74s system 114% cpu 56:58.46 total

After:

% time guida make --optimize --output=bin/guida.js src/Terminal/Main.elm
Starting downloads...

  ● andre-dietrich/parser-combinators 4.1.0
  ● elm/time 1.0.0
  ● elm/bytes 1.0.8
  ● elm/regex 1.0.0
  ● elm/virtual-dom 1.0.3
  ● elm/random 1.0.0
  ● the-sett/elm-pretty-printer 3.1.0
  ● rtfeldman/elm-hex 1.0.0
  ● fredcy/elm-parseint 2.0.1
  ● elm/html 1.0.0
  ● elm/json 1.1.3
  ● dasch/levenshtein 1.0.3
  ● elm-community/list-extra 8.7.0
  ● elm/url 1.0.0
  ● elm/core 1.0.5
  ● pilatch/flip 1.0.0
  ● elm-community/array-extra 2.6.0
  ● elm-community/basics-extra 4.1.0
  ● elm-community/maybe-extra 5.3.0
  ● guida-lang/graph 1.0.0
  ● guida-lang/glsl 1.0.0
  ● zwilias/elm-rosetree 1.5.0
  ● elm/parser 1.1.0
  ● obiloud/numeric-decimal 3.0.1
  ● elm-explorations/test 2.2.0

Dependencies ready!           
Success! Compiled 141 modules.

    Terminal.Main ───> bin/guida.js

guida make --optimize --output=bin/guida.js src/Terminal/Main.elm  157.99s user 2.57s system 108% cpu 2:28.32 total