Resolve flow errors in eslint JSX a11y (facebook#2346)

* Upgraded eslint-plugin-jsx-a11y to 5.0.3 to take advantage of
  d70ac7d7975819e7a52b85465ec67a0d93eb962a

Author: iainbeeston

package.json

@@ -37,7 +37,7 @@
     "eslint-loader": "1.7.1",
     "eslint-plugin-flowtype": "2.33.0",
     "eslint-plugin-import": "2.2.0",
-    "eslint-plugin-jsx-a11y": "5.0.1",
+    "eslint-plugin-jsx-a11y": "5.0.3",
     "eslint-plugin-react": "7.0.1",
     "extract-text-webpack-plugin": "2.1.0",
     "file-loader": "0.11.1",