Add Ruby 1.9.3 support

Thanks @Chocksy

* rebased onto latest Master and squashed
* adds support for Ruby 1.9.3; Fixes #79 

Ruby 1.9.3 has been EOL'd, and all support will end in [February 2015 ](https://www.ruby-lang.org/en/news/2014/01/10/ruby-1-9-3-will-end-on-2015/). The plan for this gem going forward is to not intentionally break 1.9.3 support, but to not continue officially supporting it past February.

Thanks