Update package.json

previous typescript version was causing build to fail

Author: wernerva

core-app/package.json

@@ -44,6 +44,6 @@
     "protractor": "~5.4.0",
     "ts-node": "~5.0.1",
     "tslint": "~5.9.1",
-    "typescript": "~2.7.2"
+    "typescript": "^2.8.0"
   }
 }