message: Fold in other Greenkeeper PRs
  Adding the changes from:
diff: "babel-eslint": "7.1.0",
  "babel-plugin-check-es2015-constants": "6.8.0",
  "babel-plugin-syntax-async-functions": "6.13.0",
  - "babel-plugin-transform-class-properties": "6.18.0",
  + "babel-plugin-transform-class-properties": "6.23.0",
  "babel-plugin-transform-es2015-arrow-functions": "6.8.0",
  "babel-plugin-transform-es2015-block-scoped-functions": "6.8.0",
  - "babel-plugin-transform-es2015-block-scoping": "6.18.0",
  - "babel-plugin-transform-es2015-classes": "6.18.0",
  + "babel-plugin-transform-es2015-block-scoping": "6.23.0",
  + "babel-plugin-transform-es2015-classes": "6.23.0",
  "babel-plugin-transform-es2015-computed-properties": "6.8.0",
  "babel-plugin-transform-es2015-destructuring": "6.22.0",
  "babel-plugin-transform-es2015-duplicate-keys": "6.8.0",
  "babel-plugin-transform-es2015-function-name": "6.9.0",
  "babel-plugin-transform-es2015-literals": "6.8.0",
  - "babel-plugin-transform-es2015-modules-commonjs": "6.18.0",
  + "babel-plugin-transform-es2015-modules-commonjs": "6.23.0",
  "babel-plugin-transform-es2015-object-super": "6.8.0",
  - "babel-plugin-transform-es2015-parameters": "6.18.0",
  + "babel-plugin-transform-es2015-parameters": "6.23.0",
  "babel-plugin-transform-es2015-shorthand-properties": "6.18.0",
  "babel-plugin-transform-es2015-spread": "6.8.0",
  "babel-plugin-transform-es2015-template-literals": "6.8.0",
  