fixed type in diag_pre_multiply in stan/math/matrix
added more tests to fvar/matrix
added crossprod to fvar/matrix
added multiply_lower_tri_self_transpose to fvar/matrix
added tcrossprod to fvar/matrix
added crossprod_test for fvar/matrix
added diag_post_multiply-test for fvar/matrix
added diag_pre_multiply_test for fvar/matrix
added multiply_lower_tri_self_transpose_test for fvar/matrix
added rep_matrix_test for fvar/matrix
added rep_row_vector_test for fvar/matrix
added rep_vector_test for fvar/matrix
added tcrossprod_test for fvar/matrix
added more tests fo fvar_matrix