Constellation/ruby-jsonchema — pull request #8 by dubek (2012-04-03 13:30:27+00:00)
Title: accept the "required" attribute instead of "optional"

According to [jsonschema IETF draft-03](http://tools.ietf.org/html/draft-zyp-json-schema-03), the `optional` attribute was replaced with the `required` attribute (default is required=false).