Implement to_json for posts.
Spec for #update
Spec for #recent
Change API for #dates and #recent

Both take parameters now. Including specs.
Merge branch 'more-methods' into next
Multiple parameters make no sense for #recent, revert to hash only.
Document all methods.
Change API to only accept needed parameters
Merge pull request #15 from ryw/next

Merge & release new version