chore(package): update babel-plugin-istanbul to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "babel-cli": "^6.16.0",
     "babel-core": "^6.26.3",
     "babel-eslint": "^10.0.2",
-    "babel-plugin-istanbul": "^5.1.4",
+    "babel-plugin-istanbul": "^6.0.0",
     "babel-plugin-transform-runtime": "^6.15.0",
     "babel-preset-latest": "^6.16.0",
     "babel-preset-stage-0": "^6.16.0",