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

Closes #21

Author: greenkeeper[bot]

package.json

@@ -114,7 +114,7 @@
     "rollup-plugin-typescript2": "^0.10.0",
     "semantic-release": "^12.2.4",
     "travis-deploy-once": "^4.3.3",
-    "ts-jest": "^22.0.0",
+    "ts-jest": "^25.5.1",
     "ts-node": "^4.1.0",
     "tslint": "^5.8.0",
     "tslint-config-prettier": "^1.1.0",