chore(package): update ts-jest to version 26.0.0

Closes #37

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "jest-mock": "23.1.0",
     "semantic-release": "15.7.2",
     "traverse": "0.6.6",
-    "ts-jest": "23.1.4",
+    "ts-jest": "26.0.0",
     "tslib": "^1.9.3",
     "tslint": "^5.10.0",
     "tslint-config-prettier": "^1.13.0",