chore(package): update jest dependencies

closes #24; closes #25; closes #26

Author: macklinu

package.json

@@ -39,17 +39,17 @@
   "homepage": "https://github.com/macklinu/danger-plugin-tslint#readme",
   "devDependencies": {
     "@types/common-tags": "^1.2.5",
-    "@types/jest": "^20.0.2",
+    "@types/jest": "^21.1.2",
     "@types/node": "^8.0.6",
     "commitizen": "^2.9.6",
     "cz-conventional-changelog": "^2.0.0",
     "danger": "^1.0.0",
     "gh-pages": "^1.0.0",
     "husky": "^0.14.1",
-    "jest": "^20.0.3",
+    "jest": "^21.2.1",
     "lint-staged": "^4.0.0",
     "semantic-release": "^6.3.6",
-    "ts-jest": "^20.0.4",
+    "ts-jest": "^21.1.2",
     "tslint": "^5.0.0",
     "typedoc": "^0.7.1",
     "typedoc-plugin-external-module-name": "^1.0.9",