Add notification.

.travis.yml

@@ -1,4 +1,13 @@
 language: c
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/8a6e4470a0cebd090344
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: never     # options: [always|never|change] default: always
+
 compiler:
   - gcc