Fixes #1

    One of them is jobid printing (user is supposed to use Python's
    logging, if needed), another is for warnings while stopping engines
    (anyway they are killed by Slurm afterwards, we just first try to
    kill them politely).

    Bugfix: now should normally work if path contains spaces.

    First more or less stable release.

    CHANGES:
    --------
    1. Add proper exception handling, while shutting down the cluster.
    2. Add ability to set a directory for the temporary files.
    3. Add helper function for quick interactive mapping without
       explisit cluster allocation in your code, as a shortcut for
       frequently used functionality. See
       `slurmified.map_interactive`.

    Generates blocking interactive map function, that creates its own
    cluster and closes it after shutdown. Intended to be a shortcut for
    frequently used functionality.

    CHANGES:
    - Add `extra_path` option to the `slurmified.Cluster` constructor to
      insert `sys.path` entries to Dask workers.
    - Default to --bokeh and --nanny instad of --no-bokeh and
      --no-nanny.

    Done by exporting PYTHONPATH before executing dask-worker command.

    It is more consistent with default Distributed behaviour. Also, it
    seems that at the moment there is some bug with start with
    --no-nanny.