Added rTorrent and libTorrent versions

Added the unstable releases for rTorrent and libTorrent. rTorrent version 0.9.2 do not respect the configuration "min_announce_interval" and is getting blacklisted.

The unstable version 0.9.3 has fixed this issue, and it's dependant on libTorrent 0.13.3.

Made some minor modifications to the README file.