Add requirements section to README

This includes a new admonition against using Ruby 1.8.7.

[ci skip]

README.rdoc

@@ -9,6 +9,27 @@ of specifying actions: get, put, post, delete.
 * Main page: http://github.com/rest-client/rest-client
 * Mailing list: rest.client@librelist.com (send a mail to subscribe).
 
+== Requirements
+
+MRI Ruby 1.9.2 and newer are supported. Alternative interpreters compatible with
+1.9.1+ should work as well.
+
+Ruby 1.8.7 is no longer supported.  That's because the Ruby 1.8.7 interpreter
+itself no longer has official support, _not_ _even_ _security_ _patches!_ If you
+have been putting off upgrading your servers, now is the time.
+({More info is on the Ruby developers'
+blog.}[http://www.ruby-lang.org/en/news/2013/06/30/we-retire-1-8-7/])
+
+The rest-client gem depends on these other gems for installation and usage:
+
+* {mime-types}[http://rubygems.org/gems/mime-types]
+* {netrc}[http://rubygems.org/gems/netrc]
+* {rdoc}[http://rubygems.org/gems/rdoc]
+
+If you want to hack on the code, you should also have {the Bundler
+gem}[http://bundler.io/] installed so it can manage all necessary development
+dependencies for you.
+
 == Usage: Raw URL
 
   require 'rest_client'

lib/restclient/util.rb

@@ -0,0 +1,15 @@
+module RestClient
+
+  # Utility methods intended for use only within RestClient
+  #
+  # @api private
+
+  module Util
+    private
+
+    def parser
+      URI.const_defined?(:Parser) ? URI::Parser.new : URI
+    end
+
+  end
+end