chore(package): update jest to version 21.0.0

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "@types/react": "^16.0.5",
     "create-react-class": "^15.6.0",
     "enzyme": "^2.8.2",
-    "jest": "^20.0.0",
+    "jest": "^21.0.0",
     "lodash": "^4.0.0",
     "most": "^1.2.2",
     "most-subject": "^5.3.0",