List regular authors under each venue

I don't think we should encourage measuring prestige by paper counts. But for individual venues (especially the smaller workshops) it would be nice to see who *regularly* publishes there. Maybe the authors sorted by number of iterations of the venue they've published in.

I whipped this up for COLING: the top ones are

```py
('junichi-tsujii', 19),
('hsin-hsi-chen', 16),
('yuji-matsumoto', 16),
('sadao-kurohashi', 15),
('christian-boitet', 14),
('ralph-grishman', 14),
('udo-hahn/unverified', 13),
('kathleen-mckeown', 13),
('min-zhang/unverified', 13),
('sophia-ananiadou', 13),
('guodong-zhou', 13),
('eva-hajicova', 12),
('aravind-joshi', 12),
('eneko-agirre', 12),
('kentaro-inui', 12),
('timothy-baldwin', 12),
('ting-liu/unverified', 12),
('yusuke-miyao', 12),
('takenobu-tokunaga', 12),
('maosong-sun', 12)
```

And for LAW:

```py
('martha-palmer', 12),
('nathan-schneider', 9),
('amir-zeldes', 7),
('nianwen-xue', 7),
('deniz-zeyrek/unverified', 7),
('nancy-ide', 7),
('stefanie-dipper/unverified', 6),
('dipti-misra-sharma', 6),
('jena-d-hwang/unverified', 6),
('vivek-srikumar', 5),
('isin-demirsahin', 5),
('keith-suderman/unverified', 5),
('udo-hahn/unverified', 5),
('karen-fort', 5),
('james-pustejovsky', 5),
```