chore(package): update rimraf to version 2.6.1

Closes #60

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -79,7 +79,7 @@
     "mocha": "3.2.0",
     "nyc": "10.0.0",
     "phantomjs-prebuilt": "2.1.14",
-    "rimraf": "2.5.4",
+    "rimraf": "2.6.1",
     "rollup": "0.38.1",
     "rollup-plugin-babel": "2.7.1",
     "sinon": "1.17.7",