chore(package): update documentation to version 4.0.0-beta15

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "babel-preset-stage-0": "6.16.0",
     "chai": "3.5.0",
     "coveralls": "2.11.15",
-    "documentation": "4.0.0-beta14",
+    "documentation": "4.0.0-beta15",
     "eslint": "3.9.1",
     "eslint-friendly-formatter": "2.0.6",
     "eslint-import-resolver-node": "0.2.3",