vl_sift: improved documentation
vl_sift: improved documentation

mylxiaoyi/vlfeat,erexhepa/vlfeat,richarddzh/vlfeat,j-bo/vlfeat,WangDequan/vlfeat,vlfeat/vlfeat,CansenJIANG/vlfeat,cvfish/vlfeat,WangDequan/vlfeat,CansenJIANG/vlfeat,WangDequan/vlfeat,mylxiaoyi/vlfeat,j-bo/vlfeat,j-bo/vlfeat,qubick/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,qubick/vlfeat,cvfish/vlfeat,rxl194/vlfeat,mylxiaoyi/vlfeat,hongzhili/vlfeat,qubick/vlfeat,CansenJIANG/vlfeat,richarddzh/vlfeat,vlfeat/vlfeat,rxl194/vlfeat,erexhepa/vlfeat,richarddzh/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,WangDequan/vlfeat,CansenJIANG/vlfeat,j-bo/vlfeat,erexhepa/vlfeat,rxl194/vlfeat,j-bo/vlfeat,hongzhili/vlfeat,mylxiaoyi/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,qubick/vlfeat,erexhepa/vlfeat,CansenJIANG/vlfeat,hongzhili/vlfeat,WangDequan/vlfeat,hongzhili/vlfeat,erexhepa/vlfeat,WangDequan/vlfeat,vlfeat/vlfeat,qubick/vlfeat,CansenJIANG/vlfeat,hongzhili/vlfeat,richarddzh/vlfeat,richarddzh/vlfeat,cvfish/vlfeat,qubick/vlfeat,cvfish/vlfeat,cvfish/vlfeat,erexhepa/vlfeat,mylxiaoyi/vlfeat,hongzhili/vlfeat,cvfish/vlfeat,richarddzh/vlfeat,mylxiaoyi/vlfeat