v0.5.4 (de facto)

Again, we haven't been good about keeping track of versions... tagging this with 0.5.4 prior to the 0.5.5 upgrade.

0.5.1.1d

Back-tagging the last long-term stable rsruby, before making any further changes. This version number is reflected in the gemspec but unfortunately is not consistent with the VERSION value in rsruby.rb.