- improved documentation of flatten and token
- added tests to reproduce issue #29
add "parserExtension" and tests
Revert "add "parserExtension" and tests"

This reverts commit 1da669f0130dbc6ed6a91d69feba0e63452375f9.
merge
Add my own parser functions. Maybe they are not need, but I don't have time to check and reflector the code, so leave it here
Merge branch 'master' of https://github.com/freewind/PetitParserDart