removed hack, added copyright header
removed hack, added copyright header

- Remove the hack which was used because of bug in n_factor_partial. n_factor_partial has also been fixed accordingly so that it doesn't return 1 as a factor.

- Added copyright header which was unintentionally removed earlier.
wbhart/flint2,jpflori/flint2,dsroche/flint2,fredrik-johansson/flint2,dsroche/flint2,fredrik-johansson/flint2,jpflori/flint2,fredrik-johansson/flint2,wbhart/flint2,dsroche/flint2,dsroche/flint2,wbhart/flint2,jpflori/flint2,jpflori/flint2