Merge pull request #5 from sudo-suhas/greenkeeper/initial

Update dependencies to enable Greenkeeper 🌴

.travis.yml

@@ -1,14 +1,29 @@
 language: node_js
+
 cache:
   directories:
     - node_modules
+
 node_js:
   - '8'
   - '7'
   - '6'
   - '4'
+
 branches:
   except:
     - /^v\d+\.\d+\.\d+$/
+
+before_install:
+# package-lock.json was introduced in npm@5
+  - npm install -g npm@5
+  - npm install -g greenkeeper-lockfile@1
+
+before_script: greenkeeper-lockfile-update
+
 script: npm run check
-after_success: npm run coverage
+
+# Only the node version 8 job will upload the lockfile
+after_script:
+  - greenkeeper-lockfile-upload
+  - npm run coverage