chore(package): update ajv-keywords to version 2.1.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -29,7 +29,7 @@
   "homepage": "https://github.com/JSONScript/jsonscript-proxy#readme",
   "dependencies": {
     "ajv": "^4.1.2",
-    "ajv-keywords": "^1.1.1",
+    "ajv-keywords": "^2.1.0",
     "body-parser": "^1.15.1",
     "express": "^4.13.4",
     "jsonscript-js": "^0.5.0",