chore(package): update jest to version 21.0.0 (#84)

Author: greenkeeper[bot]

package.json

@@ -56,7 +56,7 @@
     "html-webpack-plugin": "^2.10.0",
     "husky": "^0.14.0",
     "in-publish": "^2.0.0",
-    "jest": "^20.0.0",
+    "jest": "^21.0.0",
     "licensor": "^4.0.0",
     "lint-staged": "^4.0.0",
     "prettier": "^1.1.0",