• Add MagLev 1.1.0-dev from git
• Add Ruby 1.8.7-p370 (for those having trouble
  installing 1.8.7 with newer versions of glibc, please see
  #195 (comment))
• Update the package URL in the definition for JRuby 1.7.0-preview1
• Add JRuby 1.7.0-preview2
• Update the Rubinius 2.0.0-dev definition to use the bundled RubyGems version
  instead of installing its own
• Add an rbenv uninstall command for removing installed versions
• Improved the option parsing for ruby-build and rbenv-install so
  options may be placed in any order, and short options may be
  combined (e.g. -kv)
• Add a -l/--list option to rbenv install to list all available
  definitions
• Add a -v/--verbose option to rbenv install to invoke ruby-build in
  verbose mode
• Documented the -k/--keep flag in the command-line help for
  ruby-build and rbenv install