Add Travis notifications to Gitter.

.travis.yml

@@ -31,4 +31,10 @@ script:
     - cargo build --no-default-features --target armv7-unknown-linux-gnueabihf
 
 notifications:
-    email: false
+  email: false
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/780b178b15811059752e
+    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