Added Findery and Zappos entries to the Oneboxer::Whitelist.

Both Findery and Zappos support OpenGraph and work with the OpenGraphOneboxer. Added a comment at the top of whitelist.rb asking developers to check for OpenGraph support prior to creating a custom Onebox.
Merge pull request #948 from iancmyers/findery-onebox

Added Findery and Zappos entries to the Oneboxer::Whitelist.