chore(package): update ts-jest to version 23.1.3

Closes #4

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
     "@types/node": "^10.0.3",
     "jest": "^22.4.3",
     "standard-version": "^4.3.0",
-    "ts-jest": "^22.4.2",
+    "ts-jest": "^23.1.3",
     "typescript": "^2.8.1"
   },
   "files": [