Run coveralls on travis

Temporary using Travis CI to run coveralls for PRs

Author: Sergey Vilgelm

.travis.yml

@@ -0,0 +1,9 @@
+language: python
+python: "3.8"
+if: type = pull_request
+install:
+  - pip install ".[dev]" coveralls
+script:
+  - inv cover
+after_success:
+  - coveralls --rcfile=coverage.rc