Fix Gemfile example in README
Fix Gemfile example in README

m43nu/capistrano-mb,x44x45x41x4E/capistrano-mb,mattbrictson/capistrano-mb,mattbrictson/capistrano-mb,m43nu/capistrano-mb,x44x45x41x4E/capistrano-mb,mattbrictson/capistrano-mb,m43nu/capistrano-mb,x44x45x41x4E/capistrano-mb