chore(package): update @types/jest to version 20.0.0

Author: greenkeeper[bot]

package.json

@@ -83,7 +83,7 @@
     "@types/graphql": "^0.9.0",
     "@types/invariant": "^2.2.27",
     "@types/isomorphic-fetch": "0.0.34",
-    "@types/jest": "^19.2.0",
+    "@types/jest": "^20.0.0",
     "@types/lodash": "^4.14.36",
     "@types/node": "^7.0.5",
     "@types/object-assign": "^4.0.28",