Support downloads from Academic Torrents

[khinsen]

Academic Torrents is a file sharing service for research data that permits much larger files than any repository.

Files in Academic Torrents have no DOI, but a unique hash string that can serve as an identifier. ActivePapers would thus store the hash as a reference to the file. Given the hash, the torrent information can be obtained by downloading http://academictorrents.com/download/<hash>.torrent, which is a small text file. Feeding this to a BitTorrent client then starts the download.

For the popular BitTorrent client Transmission, there is a Python interface that should make this even easiert.