Update dependencies to enable Greenkeeper 🌴 (#327)

* chore(package): update dependencies

* docs(readme): add Greenkeeper badge

* get package.json from master

* keep badges together

README.md

@@ -1,4 +1,4 @@
-# videojs-contrib-ads [![Build Status](https://travis-ci.org/videojs/videojs-contrib-ads.svg)](https://travis-ci.org/videojs/videojs-contrib-ads)
+# videojs-contrib-ads [![Build Status](https://travis-ci.org/videojs/videojs-contrib-ads.svg)](https://travis-ci.org/videojs/videojs-contrib-ads) [![Greenkeeper badge](https://badges.greenkeeper.io/videojs/videojs-contrib-ads.svg)](https://greenkeeper.io/)
 
 The `videojs-contrib-ads` plugin provides common functionality needed by video advertisement libraries working with [video.js.](http://www.videojs.com/)
 It takes care of a number of concerns for you, reducing the code you have to write for your ad integration.