Bump coveralls from 2.0.0 to 2.1.0 (#266)

Bumps [coveralls](https://github.com/coveralls-clients/coveralls-python) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/coveralls-clients/coveralls-python/releases)
- [Changelog](https://github.com/coveralls-clients/coveralls-python/blob/master/CHANGELOG.md)
- [Commits](TheKevJames/coveralls-python@2.0.0...2.1.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-test.txt

@@ -9,7 +9,7 @@ git+git://github.com/scikit-learn-contrib/lightning.git@782c18c12961e509099ae84c
 flake8==3.8.3
 pytest==5.4.3
 pytest-mock==3.1.1
-coveralls==2.0.0
+coveralls==2.1.0
 pytest-cov==2.10.0
 
 # Other stuff