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.)
the pattern that we've been using that works pretty well:

```python
if __name__ == '__main__':
    sys.exit(main())
```

Then you can test / etc. the function you're calling