Bump Metro version to fix issue for npm users

Author: grabbou

package.json

@@ -175,8 +175,8 @@
     "graceful-fs": "^4.1.3",
     "inquirer": "^3.0.6",
     "lodash": "^4.17.5",
-    "metro": "^0.26.0",
-    "metro-core": "^0.26.0",
+    "metro": "^0.28.0",
+    "metro-core": "^0.28.0",
     "mime": "^1.3.4",
     "minimist": "^1.2.0",
     "mkdirp": "^0.5.1",
@@ -224,4 +224,4 @@
     "shelljs": "^0.7.8",
     "sinon": "^2.2.0"
   }
-}
+}