write ::then a little more clearly #cosmetic
implement Parser::seq

TODO: rename this?  It is closer to `lift` and `ap` from Applicative.
implement skip in terms of seq
inline the `then` into `map`
implement Parser.lazy

for a better way to make co-recursive parsers
restructure the json example to use lazy and seq
document `seq` and `lazy` in the README
Merge branch 'master' into feature.seq

Conflicts:
	src/parsimmon.js
implement mark and ap with seq
eliminate an unnecessary variable in ::many #cosmetic
Merge branch 'master' into feature.seq
Merge pull request #6 from jayferd/feature.seq

Feature.seq