Added
* The `Plugin.__call__` method now supports a `cleanup` argument
([92](https://github.com/watts-dev/watts/pull/92))
* Support for natural element expansion in `PluginMCNP`
([93](https://github.com/watts-dev/watts/pull/93),
[102](https://github.com/watts-dev/watts/pull/102))
* Reorganize the structure of `csv_data` generated by `PluginSAS` ([98](https://github.com/watts-dev/watts/pull/98))
Fixed
* Fix setting of executable for `PluginABCE` ([94](https://github.com/watts-dev/watts/pull/94))