feat(typescript): update typescript

Author: adamdbradley

package.json

@@ -55,7 +55,7 @@
   "dependencies": {
     "chokidar": "2.0.3",
     "jsdom": "11.11.0",
-    "typescript": "~2.9.1"
+    "typescript": "~3.1.6"
   },
   "devDependencies": {
     "@types/autoprefixer": "^9.1.0",