Fix .rvmrc file
Update ruby debugger to work with ruby 1.9.3p448
Use .ruby-version rather than .rvmrc for compatibility with rbenv etc.

Recent versions of RVM recommend this technique and warn if you use a
traditional .rvmrc.
Merge pull request #23 from dwaller/ruby_versioning

Fix up .rvmrc and move to latest 1.9.3 Ruby