Parser structure

While was reading throught postcss sources, found a moment that current parsing architecture looks

 ___________                        __________
|           |                      |          |
| Tokenizer | -> List of Tokens -> |  Parser  | -> Parser eats them and produces AST
|___________|                      |__________|

While it works fine, I am really wondering if there are any reasons for not using tokens streaming like babylon do for example, where you plug tokenizer in parser, or expose something like readNextToken?

In this manner you only scan source once, instead of scanning source and then iterating over tokens, that could provide significant performance boost.

[ai]

@tunnckoCore you could write much better tokenizer for JSON only format 😃.

[ai]

Done in orias branch