chore(package): update istanbul to version 0.4.5

https://greenkeeper.io/

package.json

@@ -46,7 +46,7 @@
   },
   "devDependencies": {
     "coveralls": "~2.11.6",
-    "istanbul": "~0.4.2",
+    "istanbul": "~0.4.5",
     "mocha": "~2.4.1",
     "mocha-lcov-reporter": "~1.2.0"
   }