itertools version mismatch for crates from registry

`criterion` 0.6 depends on `criterion-plot 0.5`. The first crate depends on `itertools 0.13` and the second (published) crate depends on `itertools 0.10`. In `master` they both depend on `itertools 0.13`. For local development, the `plot` directory is defined using `path` so the versions are consistent. It is only when downloading from the registry that the mismatch occurs. Should `criterion-plot` be released as v0.6 and `criterion` released to depend on `criterion-plot 0.6` to avoid including two versions of `itertools`?