Revert "Remove typescript dependency"

This reverts commit e545d09.

Author: Borewit

package-lock.json

@@ -40,7 +40,8 @@
     "mocha": "^3.4.2",
     "nyc": "^11.0.3",
     "ts-node": "^3.2.0",
-    "tslint": "^5.5.0"
+    "tslint": "^5.5.0",
+    "typescript": "^2.4.1"
   },
   "dependencies": {
     "es6-promise": "^4.1.1",