Eoin add domains script

Added a script to generate the "domains = ..." regex from the IANA maintained file at http://data.iana.org/TLD/tlds-alpha-by-domain.txt. (I didn't add any tests because it's a small script which has to be manually copy/pasted anyways--it's otherwise never actually used in code.)
would rather you revert this and put # noqa on the end of the really-long-regex-line