Quick fix for Ruby 2.0 breakage

According to [this discussion](https://www.ruby-forum.com/topic/4412475) the XMLRPC library included with Ruby 2.0 has a bug that makes the Content-Length header inconsistent with the actual data. This quick & dirty patch checks for a Ruby version of 2 and avoids requesting compressed content. I haven't tried on other platforms, but it shouldn't hurt.