Keep track of version of data

[cthoyt]

Inside the UniProt data directory, there's a file called ftp://ftp.uniprot.org/pub/databases/uniprot/current_release/knowledgebase/complete/reldate.txt that stores the release information. It would be good to download this and store it in a "meta" table in the PyUniProt database so it knows if there's been an update. This could be as simple as hashing the file and checking if the current hash is the same as the hash from the last update

[cebel]

New model.Version available with pyuniprot.query().version