Extract query_set_all in HTTY::Request

It's public, it's documented, it's not exported as a command but could
be. Extracted for now to be used in the `follow` method refactoring that
is to be able to call it from `HTTY::Response#follow` method
A response could be followed only once

When you follow a response more than once you will obtain the same
request this will bring back idempotency to the `follow` command in case
the `Location` value had been a relative path

Moreover it make more sense now that `follow` it's a method available on
the response object because you follow the response not the request
Merge pull request #106 from gabrielelana/issue-99

Follow state is kept inside the response

Fixes #99