chore(package): update netlify-cms to version 2.7.0

Closes #122

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "koa": "^2.3.0",
     "koa-static": "^5.0.0",
     "lint-staged": "^8.0.4",
-    "netlify-cms": "2.4.2",
+    "netlify-cms": "2.7.0",
     "nuxt": "^2.0.0",
     "prettier": "^1.7.0",
     "request-promise-native": "^1.0.4",