NGINX: CORS Access

https://gist.github.com/algal/5480916

https://gist.github.com/alexjs/4165271

https://michielkalkman.com/snippets/nginx-cors-open-configuration.html

http://enable-cors.org/server_nginx.html

http://blog.ionic.io/handling-cors-issues-in-ionic/

https://github.com/lynndylanhurley/ng-token-auth/issues/157