Added JSON output of all SLURM job numbers and added to `README.md` to
describe how to easily use the output with
[jq](https://stedolan.github.io/jq/) to pass job ids to `sacct`, `squeue`,
`scancel` or `sbatch.py --afterOk`. Fixed silly bug causing `--then`,
`--else`, and `--finally` commands not to be wrapped in a script for
submission to `sbatch`.