The threading architecture was not good at all. It was built around the HTTP part, which isn't flexible enough. Hence, the decision has been made to refactor both of those parts. This will takes 4 steps :
1. remove threads and rate limits (this commit)
2. refactor the HTTP part (the tricky part)
3. reintroduce rate-limits (quite easy)
4. introduce a new threading system (the easiest part)