fix(ci): replaced start with build at npm scripts for circle ci

Author: AnthonyNahas

Diff for: package.json

@@ -32,7 +32,7 @@
   },
   "private": true,
   "scripts": {
-    "start": "gulp build",
+    "build": "gulp build",
     "test": " gulp test",
     "demo": " gulp build:demo",
     "check-travis": " travis-status --repo=AnthonyNahas/@firebaseui/ng-bootstrap --branch=master --fail-pending || echo 'Not yet passing'"