#857 Add Creative Commons Metadata bot to robots.pm

[Ethan Blanton]

For sites with a Creative Commons badge linking back to a creativecommons.org, the Creative Commons Metadata Scraper may load pages to extract RDFa data such as authorship and original source. The bot identifies itself as:

CC Metadata Scaper http://wiki.creativecommons.org/Metadata_Scraper

(Note that the typo in 'CC Metadata Scaper' is reproduced correctly.)

Please add a matching signature to robots.pm upstream.