Allow for using Dask Cluster subclasses, such as SSHCluster or SlurmCluster,
which should make easier to deploy on clusters, supercomputers, and in
the cloud.
Re-organized how Dask distributed configuration is handled in YAML files.
The `bygen` algorithm, which is a traditional by-generational evolutionary
algorithm, now supports distributed evaluations via Dask. One can also refer
to the `parents` in pipeline operators; e.g., this is useful for
truncation selection, which needs to take the best of offspring and parents.
Broke out how YAML configuration files are handled into separate modules.
See `examples/MNIST/run.sh` for examples.
