chore(package): update jest to version 21.0.0 (#31)

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "browserify": "^14.1.0",
     "eslint": "^4.1.0",
     "husky": "^0.13.2",
-    "jest": "^20.0.1",
+    "jest": "^21.0.0",
     "lint-staged": "^4.0.0",
     "prettier": "^1.0.0",
     "semantic-release": "^7.0.1"