ratelimit: Don't process messages after disconnecting the sender for flooding
Fix for Issue #48: "You can still receive messages from disconnected users"

In the case when a user is disconnected with further messages already pending,
messages can be received from the disconnected user.
This commit will ignore all further data from any user not in ircd.users
Merge pull request #49 from ekimekim/dev/0.3

A few fixes, most notably a fix for Issue #48