Fixed a problem with copying states using `copy.copy`, which would not actually copy the data (because of the shallow-copy mechanism).
What's Changed
* Run serial tests using multiple cores by david-zwicker in https://github.com/zwicker-group/py-modelrunner/pull/45
* `copy.copy` of states now also copies state data by david-zwicker in https://github.com/zwicker-group/py-modelrunner/pull/47
**Full Changelog**: https://github.com/zwicker-group/py-modelrunner/compare/0.12.5...0.12.6