[5.0] Pinning Latest Flysystem Changes

You misunderstand. I said that you should not use `~0.whatever`, because that would mean that 0.6 and 0.7 would be included. SemVer dictates thar development minor versions can break the API.

So, as @GrahamCampbell says, `0.6.*` would be preferable for _any_ development dependency, and is nothing to do with Flysystem, or any specific changes between 0.6 and 0.7.