Allow the net-http-persistent instance to be named

I have a set of Mechanize instances, each one with its own X509 certificate.  The agents go out to a url (say `https://example.com/price?xyz`) and I get their body.

The problem is each agent will have the exact same body response as the first agent to get the URL. This is because the connection is shared.

This might be a bug/issue with `net-http-persistent.` In that it should not share connections among instances with different certificates.  I don't know, but this is my solution in the short term.  Discuss?