* Migrate to new object-persistor module
* Support updated persistor module using ES6 classes
* Update object-persistor
* Upgrade new persistor code to OError3
* Update to latest minor release for outdated packages
* Update package hashes to sha512
* Point object-persistor at master branch
Fix error in settings and tidy up tests
Remove unused variable declaration
Remove .only from tests and update eslint rules to catch it in future
Use to catch errors more safely getting md5 hash
Avoid unnecessary call to S3 to get md5 response