statistics → mathematics 关系

文件在 src/shogun/statistics	在 src/shogun/mathematics 中引用
HSIC.cpp	Statistics.h
LinearTimeMMD.cpp	Statistics.h
MMDKernelSelectionCombMaxL2.cpp	Statistics.h
MMDKernelSelectionMedian.cpp	Statistics.h
QuadraticTimeMMD.cpp	Statistics.h