Sorry about that. It's currently hosted on Heroku with limited dynos. I'm planning to move it into a VPS today.
Gemfly does a simple thing compared to bundle update. The purpose is to replace the versions of your gems in your Gemfile with the latest one. It also adds version if it doesn't have one.
If you have this gem:
gem 'rails', '~> 3.2.12'
It will become:
gem 'rails', '~> 4.2.3'
If you have:
gem 'rails'
It will become:
gem 'rails', '~> 4.2.3'
It's recommended to put versions in your Gemfile specially if you're updating to a major version.