Add support for private browsing mode

[Keith94]

Extension currently doesn't affect the tabs/url bar in private browsing.

[spikespaz]

I have this planned for the rewrite. There will be an option to either use a separate theme profile (another planned feature) or mirror the normal one for the Private mode.

When the rewrite will happen is unknown. I want to get it done fast however, because this extension has been selected as a finalist for the FF Extensions Challenge. Be sure to vote!

[Keith94]

Be sure to vote!

Done :-)

[spikespaz]

Thank you!