Updated Travis config

Author: Simon Hofmann

.travis.yml

@@ -43,9 +43,12 @@ script:
   - npm run $BUILD_TASK $TAG
 
 after_success:
-  - if [[ $TRAVIS_TAG != "" ]]; then npm run prebuild -- -u $GITHUB_TOKEN; fi
-  - if [[ $TRAVIS_TAG != "" ]]; then npm run prebuild -- -u -r electron $GITHUB_TOKEN; fi
-  - if [[ $TRAVIS_TAG != "" ]]; then npm run prebuild -- -u -r node-webkit $GITHUB_TOKEN; fi
+  - if [[ $TRAVIS_TAG != "" ]]; then
+    npm install;
+    npm run prebuild -- -u $GITHUB_TOKEN;
+    npm run prebuild -- -u -r electron $GITHUB_TOKEN;
+    npm run prebuild -- -u -r node-webkit $GITHUB_TOKEN;
+    fi
   - if [ $BUILD_TASK = 'cover' ]; then
     npm install;
     npm run codecov -- -t $CODECOV_TOKEN;