Bump metro@0.42.1

Summary:
@public

[skip-ci]

Reviewed By: mjesun

Differential Revision: D8781445

fbshipit-source-id: 32f2cbfeadbd2fb763078a046b779a16359c8bbd

package.json

@@ -167,10 +167,10 @@
     "graceful-fs": "^4.1.3",
     "inquirer": "^3.0.6",
     "lodash": "^4.17.5",
-    "metro": "^0.42.0",
-    "metro-babel-register": "^0.42.0",
-    "metro-core": "^0.42.0",
-    "metro-memory-fs": "^0.42.0",
+    "metro": "^0.42.1",
+    "metro-babel-register": "^0.42.1",
+    "metro-core": "^0.42.1",
+    "metro-memory-fs": "^0.42.1",
     "mime": "^1.3.4",
     "minimist": "^1.2.0",
     "mkdirp": "^0.5.1",