fix #11: now the default Transform ctor set the last row in Affine mode.
fix #11: now the default Transform ctor set the last row in Affine mode.

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