Make the "remember me" option work as intended

[tomhughes]

The "remember me" checkbox has not been working properly, or rather it has been treated as checked even when it isn't.

The reason is the "Gotcha" details in the check_box documentation which means that the parameter has the value "0" when unticked.

[gravitystorm]

There's the integration tests that are now failing but it's not clear to me what's going wrong with them.

[tomhughes]

It needed a slight tweak to the view because when the form is rerendered on a failed login the parameter on the redirect comes from the session so now has a different value. It should be fixed now.

[gravitystorm]

Merged, thanks!