How to change sign up confirmation link in devise?

I want to change sign up confirmation link in devise.

At the sign up time actually I got this type of link "http://localhost:3000/companies/confirmation?confirmation_token=KjN-vnApU1GBYfso2LTA"

but instead of this i want the link some what like this "http://ift.tt/1zRH1Hl"

in short I want to pass subdomain with link. so how can i do that?

Please help me out.

I am new in rails.

thanks in advance.