chore(package): update babel-plugin-transform-es2015-classes to versi…

…on 6.18.0

https://greenkeeper.io/

package.json

@@ -46,7 +46,7 @@
     "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": "6.15.0",
-    "babel-plugin-transform-es2015-classes": "6.14.0",
+    "babel-plugin-transform-es2015-classes": "6.18.0",
     "babel-plugin-transform-es2015-computed-properties": "6.8.0",
     "babel-plugin-transform-es2015-destructuring": "6.16.0",
     "babel-plugin-transform-es2015-duplicate-keys": "6.8.0",