Options become a bunch of session and connection level parameters, and requests do not need to maintain a separate Options object when they contain a body anymore, instead, objects is shared with the session, while request-only parameters get passed downwards to the request and its body. This reduces allocations of Options, currently the heaviest object to manage.
The reference for a request verb is now the string which is used
everywhere else, instead of the symbol corresponding to it. This was an
artifact from the import from httprb, and there is no advantage in it,
since these strings are frozen in most use cases, and the
transformations from symbol to strings being performed everywhere are
prooof that keeping the atom isn't really bringing any benefit.
