Add saucelabs browser testing to travis

.travis.yml

@@ -1,25 +1,22 @@
 sudo: false
 language: node_js
 node_js:
-  - "5"
-  - "6"
-  - "7"
-  - "8"
-  - "node"
-
+- '6'
+env:
+  matrix:
+  - SAUCE=true
+  global:
+    secure: fj2CF7TO1mpoM/Ft1wSIpGapoA+hqXLpUVe2iZXsGgeKVONAyh5k+s1cd9h/xGlnOmW5HyyN1M8YiTTWEjdT1yLwLYiL+cUdcW+BZBZWLN84lbjQimmDvB84ukMAdBeGz6XgSdmMYLFjZoh89qC3D0lukLZV0RdJOR8SmntwuRg=
 addons:
   chrome: stable
   firefox: latest
-
 script:
-  - npm test
-  - npm run lint
-  - npm run browser-test
-
+- npm test
+- npm run browser-test
+- npm run lint
 git:
   depth: 1
   submodules: false
-
 cache:
   directories:
-    - "node_modules"
+  - node_modules