Remove unused environment variables form tox configuration (#761)
Remove unused environment variables form tox configuration (#761)

The environment variables, CI TRAVIS TRAVIS_* TOXENV, do not influence
locust nor its tests. Keep the tox configuration minimal by excluding
them. Avoids any future unexpected differences between CI and local test
runs.
locustio/locust,mbeacom/locust,mbeacom/locust,heyman/locust,locustio/locust,locustio/locust,mbeacom/locust,mbeacom/locust,locustio/locust