FileModel#parse_metadata raises MetadataParseError.
FileModel#parse_metadata raises MetadataParseError.

This is cleaner API, and allows us to drop the FileModel#metadata?
private method, simplifying the impementation of metadata parsing
plugins.

nathandao/ginatra_dummy_2,nathandao/ginatra_dummy_2,nathandao/ginatra_dummy_2,gma/nesta,cao7113/nesta,spree/nesta,alda519/nesta