Gemfile

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.0.0'
gem 'pg'

gem 'rails-i18n'

gem 'spree', github: 'spree/spree'
gem 'spree_i18n', github: 'spree/spree_i18n'

output

deployer@debian:~/host/apps/demo_store$ bundle
Updating git://github.com/spree/spree.git
Updating git://github.com/spree/spree_i18n.git
Fetching gem metadata from https://rubygems.org/.......
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Bundler could not find compatible versions for gem "spree_core":
  In Gemfile:
    spree_i18n (>= 0) ruby depends on
      spree_core (~> 2.1) ruby

    spree (>= 0) ruby depends on
      spree_core (2.1.0.beta)
deployer@debian:~/host/apps/demo_store$ 

still, same error

gem 'spree', github: 'spree/spree', branch: 'master'
gem 'spree_i18n'

Bundler could not find compatible versions for gem "spree":
In Gemfile:
spree_i18n (>= 0) ruby depends on
spree (~> 1.1) ruby

spree (2.1.0.beta)

or this

gem 'spree', github: 'spree/spree', branch: 'master'
gem 'spree_i18n', github: 'spree/spree_i18n'

Bundler could not find compatible versions for gem "activerecord":
In Gemfile:
spree_i18n (>= 0) ruby depends on
activerecord (~> 3.0) ruby

rails (= 4.0.0) ruby depends on
  activerecord (4.0.0)

Bundler could not find compatible versions for gem "rails":
In Gemfile:
spree_i18n (>= 0) ruby depends on
rails (~> 3) ruby

rails (4.0.0)

@radar after removing Gemfile.lock and bundler cache

Bundler could not find compatible versions for gem "railties":
In Gemfile:
spree_i18n (>= 0) ruby depends on
railties (~> 3.0) ruby

coffee-rails (~> 4.0.0) ruby depends on
  railties (4.0.0)

Bundler could not find compatible versions for gem "rails":
In Gemfile:
spree_i18n (>= 0) ruby depends on
rails (~> 3) ruby

rails (4.0.0)

  source 'https://rubygems.org'

  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
  gem 'rails', '4.0.0'
  gem 'pg'

  gem 'rails-i18n'

  gem 'spree', github: 'spree/spree'
  gem 'spree_i18n', github: 'spree/spree_i18n'

  gem 'devise'
  gem 'ransack'


  gem 'sass-rails', '~> 4.0.0' # Use SCSS for stylesheets
  gem 'uglifier', '>= 1.3.0' # Use Uglifier as compressor for JavaScript assets
  gem 'coffee-rails', '~> 4.0.0' # Use CoffeeScript for .js.coffee assets and views
  gem 'jquery-rails'
  gem 'turbolinks' # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
  gem 'jbuilder', '~> 1.2' # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder


  group :production, :quality do
    gem 'unicorn'
  end

  group :doc do
    # bundle exec rake doc:rails generates the API under doc/api.
    gem 'sdoc', require: false
  end