Require toolz for dask array
Require toolz for dask array

One of the dependencies for `dask[array]` support is `toolz`. So this
adds `toolz` as an explicit dependency now that `dask` is not one.
Though `toolz` gets pulled in indirectly with `yail` as well, it makes
sense to be explicit about this one.

DudLab/nanshe_workflow,nanshe-org/nanshe_workflow