chore(package): update ts-jest to version 25.5.1

Closes #9

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
   "devDependencies": {
     "@types/jest": "^24.0.0",
     "jest": "^23.6.0",
-    "ts-jest": "^23.1.4",
+    "ts-jest": "^25.5.1",
     "typescript": "^3.0.3"
   },
   "jest": {