sacct now used instead of squeue
This change is not backward-compatible with earlier versions, hence the
major version number change.
* SLURM job status reporting was changed to use `sacct` rather than
`squeue` as a result of a pull request submitted by
[healther](https://github.com/healther). This has the advantage of being
able to show status information for jobs that have completed.
* The `squeueArgs` command line option to `slurm-pipeline.py` was removed.
* A `fieldNames` argument was added to `slurm-pipeline-status.py`. This can
be used to specify what job fields you want to see in the summary
output. The default is `State`, `Elapsed`, and `Nodelist`. You can set
`SP_STATUS_FIELD_NAMES` to a comma-separated list of job fields to set
your own default preference. See `man sacct` for the full list of field
names.
Other changes
* It is now possible to specify `error step: true` for a step that has no
dependencies. This used to be flagged as an error, but it makes sense to
allow it as the user might use `--startAfter` on the command line, and
the jobs which the no-dependency step is suppose to start after may fail.
* The `Makefile` now uses `pycodestyle` instead of `pep8` to check Python
style (this is just a new name for the `pep8` tool).
* An `--output` option was added to `slurm-pipeline.py` to allow the
specification of an output file for the JSON status. The default is to
print it to standard output.
* `SP_DEPENDENCY_ARG` is now set for all steps that don't have dependencies
if `--startAfter` is used when invoking `slurm-pipeline.py`.
* The all-step summary section of the `slurm-pipeline-status.py` output is
slightly improved, to list an overall count of jobs started and finished.