Update Rakefile to prefer Rake's built-in in #ruby method
Update Rakefile to prefer Rake's built-in in #ruby method

Remove the use of "RUBY" and instead use Rake's built-in #ruby method
to invoke a Ruby interpreter in #gem_command and #rake_command.

http://rubydoc.info/gems/rake/0.9.2/FileUtils#ruby-instance_method

jasonrudolph/stratify,jasonrudolph/stratify