depend on current parsley 0.9.2 and make sexpr-grammar/-parser more modular

This change is meant to be for the tag 0.19.3 because of it's usage by the kovasb/Nightcode project. But I think it can go into the head-version too, making a new tag for clojars maybe (?)

This change would enable use of parsley-views, but keeping your sexpr-grammar.

Since I don't see any major changes in your forks of cgrand parsley and regex, I think the dependency on parsley 0.9.2 is safe.

Best,
Joerg