Keep request body in same state as it was before read

When XmlParser was part of Rails 3, developer was able to access request.body without an issue.

At the moment in Rails 4 and using actionpack-xml_parser, request#body-s are handled different for XML and JSON  (XML needs rewind, JSON does not).

It is not hard before accessing request#body to call #rewind on it, but keeping same feel between different versions and request types, might be a good idea.