Restore babel-core bridge for Jest

Author: fatfisz

package-lock.json

@@ -20,6 +20,7 @@
     "@babel/plugin-proposal-class-properties": "7.2.3",
     "@babel/plugin-proposal-export-default-from": "7.2.0",
     "@babel/preset-env": "7.2.3",
+    "babel-core": "7.0.0-bridge.0",
     "babel-eslint": "10.0.1",
     "babel-plugin-add-module-exports": "1.0.0",
     "codecov": "3.1.0",