Replace usage of pickle in fetchrss.py

[josharrington]

Pickle is a great way to quickly store data for later use. However, it can get slow after a long time.

I created a list with 10M random torrent links and saved it with pickle. Loading, adding a new item, and dumping with pickle takes about 1.5 minutes on my machine. It also created a pickle file that is 690MB which means it will take up at least that much memory.

Would using sqlite be a faster way of handing torrent history? Would it use less memory?