.travis.yml: don't run any build job on pushes to master

.travis.yml

@@ -1,5 +1,9 @@
 language: node_js
 
+branches:
+  except:
+  - master
+
 node_js:
   - "node"
 
@@ -14,7 +18,6 @@ before_install:
 
 script:
   - 'echo "DEBUG: $TRAVIS_BRANCH - $TRAVIS_EVENT_TYPE - $TRAVIS_PULL_REQUEST"'
-  - 'if [ "$TRAVIS_BRANCH" == "master" ]; then make check_syntax_full; fi'
   - 'if [[ "$TRAVIS_BRANCH" == "master" && "$TRAVIS_EVENT_TYPE" == "cron" ]]; then make check_all; fi'
   - 'if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then make check_pr; fi'