Bump coveralls from 2.1.2 to 2.2.0

Bumps [coveralls](https://github.com/coveralls-clients/coveralls-python) from 2.1.2 to 2.2.0.
- [Release notes](https://github.com/coveralls-clients/coveralls-python/releases)
- [Changelog](https://github.com/coveralls-clients/coveralls-python/blob/master/CHANGELOG.md)
- [Commits](https://github.com/coveralls-clients/coveralls-python/compare/2.1.2...2.2.0)

Signed-off-by: dependabot[bot] <support@github.com>

requirements-dev.txt

@@ -3,7 +3,7 @@
 -r requirements-plot.txt
 -r requirements-hyperopt.txt
 
-coveralls==2.1.2
+coveralls==2.2.0
 flake8==3.8.4
 flake8-type-annotations==0.1.0
 flake8-tidy-imports==4.1.0