Update dependencies to enable Greenkeeper 🌴 (#2113)

* chore(package): update dependencies

* docs(readme): add Greenkeeper badge

README.md

@@ -7,6 +7,8 @@ Follow the link for more information: [http://c3js.org](http://c3js.org/)
 
 ## Tutorial and Examples
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/c3js/c3.svg)](https://greenkeeper.io/)
+
 + [Getting Started](http://c3js.org/gettingstarted.html)
 + [Examples](http://c3js.org/examples.html)
 

package.json

@@ -60,7 +60,7 @@
     "node-sass": "^4.5.3",
     "node-static": "^0.7.9",
     "nodemon": "^1.11.0",
-    "rollup": "^0.41.6",
+    "rollup": "^0.45.2",
     "rollup-plugin-babel": "^2.7.1",
     "uglify-js": "^3.0.15",
     "watchify": "^3.9.0"