add claim.third_party? method
Merge pull request #47 from Fullscreen/feature/claim-third-party

add claim.third_party? method
Fix broken test: a field is not required
Merge branch 'fix-broken-test'
Previously Video#update could only update snippet parameters such
as title, description. After this commit, status parameters can be
updated as well.

Unfortunately, YouTube does not let users update most of the status
parameters through the API: only privacyStatus, publicStatsViewable
and publishAt can indeed be updated.