Echo serious astro-ph twitter accounts

E.g. @AstroPHYPapers, @Awesome_Ph, ...

The nicest way to do this would be to store incoming tweets to echo in a fifo queue (fixed length to avoid getting stale), then [periodically](http://stackoverflow.com/questions/8600161/executing-periodic-actions-in-python) (hourly?) pop the next one and tweet the improved version.
