[Engine-Twitter] Simplify TwitterProtocolManager.SortTimeline()
[Engine-Twitter] Implemented "timeline" command

This command can also receive more than one user (separated by commas),
in the same way you can join many IRC channels at the same time, but
with the added feature that the timelines will be joined in just one
groupchat window.
Merge pull request #132 from knocte/timeline-command