make BenchTimer compatible with 2.0 branch
make BenchTimer compatible with 2.0 branch

rotorliu/eigen,mjbshaw/Eigen,madlib/eigen_backup,mjbshaw/Eigen,madlib/eigen_backup,madlib/eigen_backup,rotorliu/eigen,rotorliu/eigen,mjbshaw/Eigen,madlib/eigen_backup,rotorliu/eigen,mjbshaw/Eigen