Infinite redirect when domain has HSTS

[sammacbeth]

When loading a dat site which has HSTS, we can get a conflict between the browser, which tries to prevent a insecure load on this domain, and this extension, which tries to downgrade the connection in order to proxy over dat. This leads to an infinite redirect.

One possible solution would be to detect the browsers https upgrade redirect, then fallback to the raw dat url for this site.

[sammacbeth]

Fixed by ac9c96b