fix(travis): Only trigger branch builds for master

Signed-off-by: Ingo Bürk <ingo.buerk@tngtech.com>

Author: Airblader

.travis.yml

@@ -2,6 +2,9 @@ language: node_js
 dist: trusty
 node_js:
     - lts/*
+branches:
+    only:
+        - master
 notifications:
     email:
         on_success: change
@@ -15,4 +18,4 @@ script:
     - yarn run demo:build:prod
     - yarn run api-docs:build
 after_success:
-    - yarn run codecov
+    - yarn run codecov