chore(travis): avoid double builds on PRs

Author: gr2m

.travis.yml

@@ -11,8 +11,12 @@ script: npm run $COMMAND
 before_script:
   - npm prune
 after_success:
-  - npm run test:coverage && npm run test:coverage:upload
+  - npm run coverage:upload
   - npm run semantic-release
+
+# Trigger a push build on master and greenkeeper branches + PRs build on every branches
+# Avoid double build on PRs (See https://github.com/travis-ci/travis-ci/issues/1147)
 branches:
-  except:
-    - /^v\d+\.\d+\.\d+$/
+  only:
+    - master
+    - /^greenkeeper.*$/