Add travis.yml and configure npm test

.travis.yml

@@ -0,0 +1,11 @@
+language: node_js
+node_js:
+  - "iojs"
+  - "5"
+  - "6"
+  - "7"
+  - "8"
+
+cache:
+  directories:
+    - "node_modules"

package.json

@@ -26,7 +26,8 @@
     "password"
   ],
   "scripts": {
-      "gulp": "gulp"
+      "gulp": "gulp",
+      "test": "gulp test"
   },
   "author": "Slava Bacherikov",
   "license": "GPL-3.0",