upgrade image-size version fix caculate webp image size bugs

Summary:
When I try to use webp for app. But some webp images get an error message `unsupported file type` by image-size@0.3.5.

And I in image-size repo I found a issue https://github.com/image-size/image-size/issues/65.
This is the same problem.

And try image-size^0.5.1 the error fixed.

![image](https://cloud.githubusercontent.com/assets/13161470/23597366/403a3070-026d-11e7-8666-f4357f1eee73.png)
Closes https://github.com/facebook/react-native/pull/14238

Reviewed By: davidaurelio

Differential Revision: D5145534

Pulled By: javache

fbshipit-source-id: a2aeeae19e928ffefbd0b32501d34069ed37386d

package.json

@@ -23,6 +23,7 @@
     "eslint-plugin-react": "^7.0.1",
     "flow-bin": "^0.46.0",
     "glob": "^7.1.1",
+    "image-size": "^0.5.1",
     "istanbul-api": "^1.1.0",
     "istanbul-lib-coverage": "^1.0.0",
     "jest": "^19.0.2",

yarn.lock

@@ -1937,6 +1937,10 @@ ignore@^3.2.0:
   version "3.3.3"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.3.tgz#432352e57accd87ab3110e82d3fea0e47812156d"
 
+image-size@^0.5.1:
+  version "0.5.5"
+  resolved "https://registry.yarnpkg.com/image-size/-/image-size-0.5.5.tgz#09dfd4ab9d20e29eb1c3e80b8990378df9e3cb9c"
+
 imurmurhash@^0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/imurmurhash/-/imurmurhash-0.1.4.tgz#9218b9b2b928a238b13dc4fb6b6d576f231453ea"