Update Travis config

Author: taion

.travis.yml

@@ -1,16 +1,23 @@
+sudo: false
+
 language: node_js
 node_js:
-  - "4"
-sudo: false
+  - stable
+
+cache:
+  directories:
+    - node_modules
+
 before_script:
   - wget http://www.browserstack.com/browserstack-local/BrowserStackLocal-linux-x64.zip
   - unzip BrowserStackLocal-linux-x64.zip
   - "./BrowserStackLocal $BROWSER_STACK_ACCESS_KEY localhost,8001,0 > /dev/null &"
   - sleep 10
+
 after_success:
   - cat ./coverage/lcov.info | ./node_modules/codecov.io/bin/codecov.io.js
   - cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js
+
 branches:
-  except:
-  - latest
-  - "/^v\\d/"
+  only:
+    - master