Add gitter webhook to travis config

Author: olizilla

.travis.yml

@@ -7,4 +7,12 @@ before_install:
   - npm install -g gulp
 
 script:
-  - gulp
+  - gulp
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/fb4976f83539730820f1
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: false     # default: false