chore(package): update ts-jest to version 25.4.0

Closes #43

Author: greenkeeper[bot]

package.json

@@ -122,7 +122,7 @@
     "rollup-plugin-typescript2": "^0.21.0",
     "semantic-release": "^15.9.16",
     "travis-deploy-once": "^5.0.9",
-    "ts-jest": "^24.0.0",
+    "ts-jest": "^25.4.0",
     "ts-node": "^8.0.2",
     "tslint": "^5.11.0",
     "tslint-config-prettier": "^1.15.0",