Ipyslurm

* Option to repeat tail output, true by default.
* Replace carriage return with newline in tail.
* Make ipywidgets a a soft dependency.
* Various improvements to the CI configuration.
* Specify minimum dependency versions, use conda-forge.
* Do not overload repr, provide slurm.server as a property.
* Handle paramiko SSH exceptions, do not load system SSH keys.

* New example notebooks demonstrating basic and advanced use from Python.
* Separate stail from sbatch to match the Python interface.
* Allow passing slurm instance to magics.
* Prevent output flicker.
* Reintroduce login support for MARCC and potentially other clusters.
* Various fixes for errors introduced in previous release.

* Backwards incompatible changes, e.g., renamed magics.
* Refactor slurm module for standalone use.
* Dropped custom logic to support MARCC.

* Support `ls`, `mkdir`, and `rmdir` in `sftp` cell magic.
* Various fixes, including escaping paths with spaces.
* Continuous integration using GitHub Actions.

* New `sshell` line magic, supersedes `sinteract`.
* Block bash commands to avoid flooding server on period calls.
* Project is properly marked as an IPython extension.

* New `sftp` remote commands `rm` and `rmdir`.
* New `sftp` local commands `lrm` and `lrmdir`.
* New `sbatch` line magic.
* Minimum required `paramiko` is v2.5.