Revert "update ruby to 1.9.3-p392 and associated devkit. see http://www.ruby-lang.org/en/news/2013/02/22/ruby-1-9-3-p392-is-released for more info"

This reverts commit e1a7da511249d03aad787fdc481e4ebe3809be81.
Merge pull request #35 from ilude/ruby-revert

Revert "update ruby to 1.9.3-p392 and associated devkit.