chore(package): update jest dependencies

closes #28; closes #29; closes #30

Author: macklinu

package.json

@@ -35,17 +35,17 @@
     "node": ">= 4.0.0"
   },
   "devDependencies": {
-    "@types/jest": "^20.0.2",
+    "@types/jest": "^21.1.4",
     "@types/node": "^8.0.6",
     "commitizen": "^2.9.6",
     "cz-conventional-changelog": "^2.0.0",
     "gh-pages": "^1.0.0",
     "husky": "^0.14.1",
-    "jest": "^20.0.4",
+    "jest": "^21.2.1",
     "lint-staged": "^4.0.0",
     "prettier": "^1.7.0",
     "semantic-release": "^6.3.6",
-    "ts-jest": "^20.0.5",
+    "ts-jest": "^21.1.3",
     "tslint": "^5.4.2",
     "tslint-config-prettier": "^1.5.0",
     "typedoc": "^0.7.1",