Run basic `bundle install` checks with JRuby
Run basic `bundle install` checks with JRuby

We don't run JRuby checks for every pull request because of not being
stable enough. However, we can make sure things like `bundle install`
work for every PR, which should be stable enough and will help us catch
some issues earlier.

deivid-rodriguez/activeadmin,deivid-rodriguez/activeadmin,activeadmin/activeadmin,activeadmin/activeadmin,activeadmin/activeadmin,deivid-rodriguez/activeadmin