chore(package): update typescript to version 2.1.5

https://greenkeeper.io/

package.json

@@ -79,7 +79,7 @@
     "tsify": "^3.0.0",
     "tslint": "4.3.1",
     "typedoc": "^0.5.0",
-    "typescript": "^1.8.10",
+    "typescript": "^2.1.5",
     "typings": "^2.0.0"
   }
 }