chore(package): update ts-jest to version 22.4.4

Closes #30

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "jest": "^21.2.1",
     "lint-staged": "^4.0.0",
     "semantic-release": "^6.3.6",
-    "ts-jest": "^21.1.2",
+    "ts-jest": "^22.4.4",
     "tslint": "^5.0.0",
     "typedoc": "^0.7.1",
     "typedoc-plugin-external-module-name": "^1.0.9",