Build Ruby 2 CentOS appliance

This is now ready for review and merge.

TODO:

- [x] Get ruby-install built
- [x] Install ruby 2.0.0
- [x] Verify bundling works (ruby environment is properly loaded)
- [x] See if we can build qpid_messaging or punt into a followup PR [#953]
- [x] Verify building of shared objects works
- [x] Variablize the ruby version (ruby 2.0.0-p576) - can't do until ruby-install honors --update to update it's own list of rubies
- [x] Remove references to my fork/repo/branches

See #837
Does this mean these are "dependencies of ruby-install itself", or "dependencies of the rubies built by ruby-install".  Can we change the comment to be clearer.  Also, doesn't ruby-install do the dependency installation itself so we do have to do it?