update dragonfly version to ~>1.0

I have updated dragonfly versions to support the current version of [dragonfly-s3_data_store](https://github.com/markevans/dragonfly-s3_data_store). This will break the current version of [activeadmin-wysihtml5](https://github.com/stefanoverna/activeadmin-wysihtml5), which I have also patched to support dragonfly ~>1.0