Reverting https://github.com/yaml/pyyaml/pull/74

Revert "Make pyyaml safe by default."

This reverts commit bbcf95fa051fdba9bbf879332e2f7999b195cf95.
This reverts commit 7b68405c81db889f83c32846462b238ccae5be80.
This reverts commit 517e83e8058e9d6850ab432ef22d84c2ac2bba5a.
12 files changed