bump to 3.2-beta1 (3.1.91)
bump to 3.2-beta1 (3.1.91)

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