Support multiprocessing in tests

.coveragerc

+[run]
+concurrency=multiprocessing
\ No newline at end of file

tox.ini

@@ -5,6 +5,8 @@ envlist = py36
 exclude = venv,.tox
 
 [testenv]
+setenv = 
+    COVERAGE_PROCESS_START=.coveragerc
 deps =
     coverage
     flake8
@@ -13,6 +15,7 @@ deps =
 commands =
     coverage erase
     coverage run --source brian_dashboard_manager -m py.test {posargs}
+    coverage combine
     coverage xml
     coverage html
     coverage report --fail-under 75