[Request] Make proxy usage optional through an attribute

[The-MAZZTer]

It looks like you could call .load directly and do this but it would be nice to have this possible with the src= value as well. In fact the proxies could also be configurable in this manner as well.

For example adding a proxies attribute with a space-separated list of proxies (if you make it blank, no proxies are used).

This would be useful for using your own proxy, or in environments where a proxy is not required for CORS bypass (eg Chrome extension pages with the proper host_permissions).