Make win32 binary gems only support Ruby 1.9

Ruby 1.8 was officially retired on Jun 30, 2013: http://www.ruby-lang.org/en/news/2013/06/30/we-retire-1-8-7/
Version bump for win32 gem repackaging

Attempted fix for https://github.com/codahale/bcrypt-ruby/issues/72
Version bump for 3.1.1 official release