0.2.3-beta: YAML updates and small bug fixes:

• add ymo_yaml_doc_get / ymo_yaml_doc_vget
• fix defaults if not set in config
• split WSGI config into header file (TEMPORARY HACK. Will tidy)
• reset optind after parse if we're going to parse more than once

TODO: Just discovered the yaml_document_t portion of the API in yaml.h.
Should migrate from ymo_yaml_doc_t to yaml_document_t.