Meta: update .travis.yml

To adapt to whatwg/whatwg.org#119 and whatwg/whatwg.org#137.

Author: foolip

.travis.yml

@@ -1,14 +1,16 @@
-dist: trusty
 language: generic
 
 env:
   global:
     - ENCRYPTION_LABEL="f5b0eb183bc9"
-    - DEPLOY_USER="annevankesteren"
 
 script:
   - curl --remote-name --fail https://resources.whatwg.org/build/deploy.sh && bash ./deploy.sh
 
+branches:
+  only:
+    - master
+
 notifications:
   email:
     on_success: never