set domain for cookies to use base domain

[amrnt]

No description provided.

[pirkka]

Thanks, this helped me to persist user's mobile/desktop choice across different subdomains.

[amrnt]

Thank you! I'm looking forward for merging this /cc: @jistr

[jistr]

@amrnt Heya, sorry for the delay ;) This looks like a good thing to have. Would you mind writing some specs for it? https://github.com/jistr/mobvious/blob/master/spec/mobvious/strategies/cookie_spec.rb

Also I'd prefer if you could change return unless host !~ to return if host =~, but that's not a blocker.

Looks good :)