Fix broken Travis tests (#41)

Fixed: Make Node version fixed on Travis, switch to `npm test` command,
			 so we use package.json Gulp 3.9.1 version

Author: Jastrzebowski

.travis.yml

@@ -1,7 +1,5 @@
 language: node_js
 node_js:
-  - "node"
-  
-before_script:
-  - npm install -g gulp
-script: gulp test
+  - "9"
+
+script: npm test