Added NonNegativeInteger.
Added NonNegativeInteger.

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