The :mongoid group does not work in JRuby so the group
is only defined for the platform: 'ruby'.
In addition installing ruby-debug in JRuby is a manual process so
only include the dependency if we are using the platform: 'ruby'
Here are the steps necessary to run the devise tests in JRuby
rvm install jruby
rvm use jruby@devise --create
gem install bundler --pre
gem install jeweler