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

Closes #30

Author: greenkeeper[bot]

package.json

@@ -100,7 +100,7 @@
     "rollup-plugin-typescript2": "^0.15.1",
     "semantic-release": "^15.6.0",
     "travis-deploy-once": "^5.0.0",
-    "ts-jest": "^24.0.0",
+    "ts-jest": "^25.2.1",
     "ts-node": "^8.0.3",
     "tslint": "^5.8.0",
     "tslint-config-prettier": "^1.1.0",