chore(package): update ts-jest to version 25.2.1

Closes #25

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "@types/jest": "24.0.23",
     "@types/node": "12.12.14",
     "jest": "24.9.0",
-    "ts-jest": "24.2.0",
+    "ts-jest": "25.2.1",
     "tslint": "5.20.1",
     "typescript": "3.7.2",
     "version-bump-prompt": "5.0.6"