Only run coverage when all builds complete

.travis.yml

@@ -38,6 +38,7 @@ matrix:
 env:
   global:
     - PYTHONUNBUFFERED=True
+    - COVERALLS_PARALLEL=true
 before_install:
     - openssl aes-256-cbc -K $encrypted_b3fcf6d0737c_key -iv $encrypted_b3fcf6d0737c_iv
             -in credentials.tar.gz.enc -out credentials.tar.gz -d
@@ -74,7 +75,7 @@ install:
     - pip install coveralls
     - pip install codecov
 script:
-    - tox -r -e $TOX_ENV
+    - tox -e $TOX_ENV
 after_script:
     - |
       case "$TRAVIS_EVENT_TYPE" in
@@ -95,3 +96,5 @@ after_script:
            coveralls & codecov & wait
            ;;
       esac
+notifications:
+    webhooks: https://coveralls.io/webhook