Add potential `mysqldump` and `zip` locations

Originally: https://github.com/humanmade/hm-backup/commit/15b9a4cefc7fb54c5dc09a2ecc6d8f37c104b0e2
Some functions that can also be disabled by suhosin

Originally https://github.com/humanmade/hm-backup/commit/f80f22f396d4dd996b34b8b82643334a49a5881e
Merge pull request #80 from humanmade/update-hm-backup-80

Update HM backup to latest