chore(package): update jest to version 21.0.2

Closes #27

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "flow-bin": "^0.43.1",
     "flow-coverage-report": "^0.3.0",
     "graphql": "^0.9.2",
-    "jest": "^19.0.2",
+    "jest": "^21.0.2",
     "jest-diff": "^19.0.0",
     "jest-matcher-utils": "^19.0.0",
     "pretty-format": "^19.0.0"