Update .travis.yml

Author: LowPowerLab

.travis.yml

@@ -15,4 +15,6 @@ addons:
 before_install:
   - npm -g install npm@latest
 install:
-  - npm install --unsafe-perm --build-from-source
+  - npm install --unsafe-perm --build-from-source
+script:
+  - node gateway.js