chore(package): update ts-jest to version 22.4.1

Closes #35

Author: greenkeeper[bot]

package.json

@@ -45,7 +45,7 @@
     "lint-staged": "^4.0.0",
     "prettier": "^1.7.4",
     "semantic-release": "^6.3.6",
-    "ts-jest": "^21.1.3",
+    "ts-jest": "^22.4.1",
     "tslint": "^5.4.2",
     "tslint-config-prettier": "^1.6.0",
     "typedoc": "^0.7.1",