Add a clearer description of the settings page to avoid excessive server load

The Readme file of Responsive Images and Styles should add some information about the various options on admin/config/media/resp_img/settings - particularly on the "Reload on resize" option. I have found out that if this is set to Yes and the browser window is resized, it apparently reloads the entire page upon resizing of the browser window. What was not so clear was this "use wisely!" in the description of this setting.

Because what we could reproduce if this switch is set to "Yes" in our environment (FastCGI/Apache2) was that upon resizing of the browser window, the process load of the server went sky rocket high up - sometimes forcing us to issue a server restart command through the Remote Access Console even because the process load went up to even 300% in our environment if "Reload on resize" was set to Yes.

I wouldn't want to turn this issue into a bug but rather leave it as a Documentation Task since Respinsive Images and Styles Version 2.x as well as the preferred Picture module don't seem to show this behaviour. In the meantime a short notice on what the various settings options really do and why you should use "Reload on Resize" wisely as it is already stated in the interface would probably reduce the risk of people running into the same difficulty as we did, searching nearly 2 weeks until we found out what had caused it ;-)))

Nontheless: EXCELLENT work!