Experiment - eliminate creation of nested tuples

[sergei-shabanau]

Connects #75

Ultimately I am pursuing the following flow:

1. Have user-defined AST1 in terms of Grammar.GADT
2. Rewrite / Optimize AST1 into another AST2 expressed as low level GADT
3. Compile resulting AST2 into parser/printer functions

My biggest concern is the lost type safety at step 2 with my current approach, thus I'd like to get some advise with implementation approach I am taken.

I've added inline comments to ease the discussion.

[codecov-io]

Codecov Report

Merging #78 into master will decrease coverage by 8.19%. The diff coverage is 0.00%.

@@             Coverage Diff             @@
##            master      #78      +/-   ##
===========================================
- Coverage   100.00%   91.80%   -8.20%     
===========================================
  Files            3        3              
  Lines          269      293      +24     
  Branches         5        6       +1     
===========================================
  Hits           269      269              
- Misses           0       24      +24     

Impacted Files	Coverage Δ
...ain/scala/org/spartanz/parserz/ParsersModule.scala	90.87% <0.00%> (-9.13%)	:arrow_down:

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