chore(package): update @types/jest to version 21.1.0 (#11)

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
   },
   "homepage": "https://github.com/serviejs/servie-send",
   "devDependencies": {
-    "@types/jest": "^20.0.0",
+    "@types/jest": "^21.1.0",
     "@types/node": "^8.0.0",
     "jest": "^21.0.0",
     "rimraf": "^2.5.4",