metro-bundler: upgrade

Reviewed By: cpojer

Differential Revision: D5190525

fbshipit-source-id: f92da16733f95475650db2395c76495cce862d32

package.json

@@ -182,7 +182,7 @@
     "left-pad": "^1.1.3",
     "lodash": "^4.16.6",
     "merge-stream": "^1.0.1",
-    "metro-bundler": "^0.7.3",
+    "metro-bundler": "^0.7.4",
     "mime": "^1.3.4",
     "mime-types": "2.1.11",
     "minimist": "^1.2.0",