chore(package): update typescript to version 1.8.9

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -20,7 +20,7 @@
     "atom-package-deps": "4.0.1",
     "resolve": "1.1.7",
     "tslint": "3.6.0",
-    "typescript": "1.8.7"
+    "typescript": "1.8.9"
   },
   "readmeFilename": "README.md",
   "bugs": {