fix(package): update core-js to version 3.2.0

Closes #43

Author: greenkeeper[bot]

Diff for: package.json

@@ -22,7 +22,7 @@
     "@angular/platform-browser-dynamic": "^5.0.2",
     "@angular/router": "^5.0.2",
     "bootstrap": "^3.3.7",
-    "core-js": "^2.4.1",
+    "core-js": "^3.2.0",
     "rxjs": "^5.4.1",
     "zone.js": "^0.8.14"
   },