update .travis.yml for webhooks

.travis.yml

@@ -1,12 +1,21 @@
 language: python
+
 python:
     - "3.4"
+
 install:
     - pip install -r src/requirements_dev.txt
+
 before_script:
     - cd src
+
 script:
     - flake8 c3nav
     - isort -c -rc .
     - python manage.py collectstatic --noinput
     - python manage.py compress
+
+notifications:
+    webhooks:
+        urls:
+            - https://hooks.c3nav.de