Bug fixed (08/11/2014)

1. fix the bug in the information gain formula
Class: GetInformationGain
Method: getIGMatirix
Line: 149
double IG = this.entropy + pw * getLogSum(pcwf) +
(1-pw)*getLogSum(pcw_bf);
second * was amended from “+”
2. Filter the useless characters other than “A~Z” And “-“