added derivation notes for the cdr ratio getter
added derivation notes for the cdr ratio getter

ronaldpereira/WoWAnalyzer,anom0ly/WoWAnalyzer,yajinni/WoWAnalyzer,WoWAnalyzer/WoWAnalyzer,fyruna/WoWAnalyzer,sMteX/WoWAnalyzer,Juko8/WoWAnalyzer,FaideWW/WoWAnalyzer,yajinni/WoWAnalyzer,WoWAnalyzer/WoWAnalyzer,anom0ly/WoWAnalyzer,anom0ly/WoWAnalyzer,FaideWW/WoWAnalyzer,sMteX/WoWAnalyzer,fyruna/WoWAnalyzer,fyruna/WoWAnalyzer,FaideWW/WoWAnalyzer,ronaldpereira/WoWAnalyzer,sMteX/WoWAnalyzer,yajinni/WoWAnalyzer,Juko8/WoWAnalyzer,ronaldpereira/WoWAnalyzer,yajinni/WoWAnalyzer,anom0ly/WoWAnalyzer,WoWAnalyzer/WoWAnalyzer,Juko8/WoWAnalyzer