Update tox.ini

Author: DrFaust92

tox.ini

@@ -37,6 +37,7 @@ commands =
     py{27,34}: coverage run --source aws_xray_sdk -m py.test tests --ignore tests/ext/aiohttp --ignore tests/ext/aiobotocore --ignore tests/test_async_local_storage.py --ignore tests/test_async_recorder.py
     codecov
     py{35,36,37}: coverage run --source aws_xray_sdk -m py.test tests
+    codecov
 
 setenv =
     DJANGO_SETTINGS_MODULE = tests.ext.django.app.settings