Changed nick class to use __slots__.
Changed nick class to use __slots__.

ProgVal/Limnoria-test,raboof/supybot,mazaclub/mazabot-core,buildbot/supybot,jeffmahoney/supybot,prashantpawar/supybot-rothbot,Ban3/Limnoria,haxwithaxe/supybot,Ban3/Limnoria,ProgVal/Limnoria-test,frumiousbandersnatch/supybot-code,mazaclub/mazabot-core,kblin/supybot-gsoc