* Add notes about safe uses of twox * Update frame/grandpa/src/lib.rs Co-authored-by: Nikolay Volf <nikvolf@gmail.com> * Update frame/elections/src/lib.rs * Apply suggestions from code review Co-authored-by: Gavin Wood <gavin@parity.io> Co-authored-by: Nikolay Volf <nikvolf@gmail.com>