Allow to use ES6 code
Rewrite tests from CoffeeScript to ES6
Fix comma
Remove deprecated options support
Convert SyntaxError to ES6
Convert vendor to ES6
Convert list to ES6
Convert Result to ES6
Convert Comment to ES6
Convert Raw to ES6
Convert postcss to ES6
Convert Root to ES6
Convert PreviousMap to ES6
Convert MapGenerator to ES6
Fix integration test for ES6
Rewrite parser to ES6
Rewrite Rule to ES6
Convert Declaration to ES6
Convert AtRule to ES6
Convert Node to ES6