Additional unit tests.
Initialized first_class_polymorphism from algorithm_w.
Implemented AST, printing, parser and unification for first_class_polymorphism.
Implemented functions subsume, instantiate and generalize.
Implemented type inference for first-class polymorphism.
Implemented type inference for n-ary function call, fixes.
Added rigid type annotations.
Simplified code.
Merge branch 'dev'
More tests.
Added README for first-class polymorphism.
Initialized a type inference algorithm that propagates types for first-class polymorphism.
Implemented a type inference algorithm that propagates types for first-class polymorphism.
Bugfix in README.md.