Update tested nodejs versions in .travis.yml

See See https://github.com/nodejs/Release

Author: gkubisa

.travis.yml

@@ -1,9 +1,9 @@
 language: node_js
 node_js:
-  - 6
-  - 5
-  - 4
-  - 0.10
+  - "9"
+  - "8"
+  - "6"
+  - "4"
 script: "npm run jshint && npm run test-cover"
 # Send coverage data to Coveralls
 after_script: "cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js"