Added examples for casting, made better examples for Maps
Added examples for casting, made better examples for Maps

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