chore(package): update jest-diff to version 20.0.3

Closes #26

Author: greenkeeper[bot]

package.json

@@ -54,7 +54,7 @@
     "flow-coverage-report": "^0.3.0",
     "graphql": "^0.9.2",
     "jest": "^19.0.2",
-    "jest-diff": "^19.0.0",
+    "jest-diff": "^20.0.3",
     "jest-matcher-utils": "^19.0.0",
     "pretty-format": "^19.0.0"
   },