cap production deploy ruby on rails - ruby-on-rails

Question

I tried to deploy the ruby on rails project from a github folder. However, I got such an error when I run cap production deploy
/home/deploy/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in
'require': cannot load such file -- capistrano/cli (LoadError) from /home/deploy/.rbenv/
versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in 'require'
from /usr/bin/cap:3:in '<main>'
I have deploy.rb starting with:
# config valid only for Capistrano 3.1
lock '3.1.0'
And I installed Capistrano v.3.1 with the following command-line:
gem install capistrano -v 3.1.0
Anybody has ideas why I still got an error?
Attached Gemfile:
source 'https://rubygems.org'
gem 'rails', '4.1.0'
# Frontend
gem 'simple_form'
gem 'nested_form', github: 'ryanb/nested_form'
gem 'turbolinks'
gem 'bootstrap-sass', '~> 3.2.0'
gem 'kaminari'
# Javascript
gem 'gon'
gem 'angularjs-rails'
gem 'selectize-rails'
gem 'js-routes'
# Backend
gem 'pg'
gem 'mongoid', github: 'mongoid/mongoid'
gem 'mongoid_geospatial'
gem "active_model_serializers"
gem 'devise'
gem 'state_machine'
gem "rolify"
gem "pundit"
gem 'enumerize'
gem 'simple-rss'
gem 'tweetstream'
gem 'swagger-docs', path: "vendor/gems/swagger-docs-0.1.5"
gem 'wkhtmltopdf-binary'
gem 'wicked_pdf'
gem 'paper_trail', '~> 3.0.3'
# Temporary
gem 'faker'
gem 'factory_girl_rails'
# Asset gems
gem 'haml-rails'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.0.0'
gem 'jquery-rails'
gem 'sass-rails', '~> 4.0.3'
gem 'compass-rails'
group :development do
gem 'spring' # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
gem 'switch_user'
gem 'better_errors'
gem 'binding_of_caller'
gem 'sextant'
gem 'guard-livereload', require: false
gem 'capistrano', '~> 3.1.0'
gem 'capistrano-bundler', '~> 1.1.2'
gem 'capistrano-rails', '~> 1.1.1'
gem 'capistrano-rbenv', github: "capistrano/rbenv"
end
group :test do
gem 'rspec-rails'
gem 'spring-commands-rspec'
gem 'guard-rspec'
gem 'fuubar'
gem 'capybara'
gem 'capybara-webkit'
gem 'capybara-email'
gem 'capybara-screenshot'
gem 'database_cleaner'
end
group :test, :darwin do
gem 'rb-fsevent'# if `uname` =~ /Darwin/
end
group :development, :test do
gem 'pry-rails'
gem 'pry-remote'
end
# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby
# Use unicorn as the app server
# gem 'unicorn'
# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development
# Use debugger
# gem 'debugger', group: [:development, :test]
Thanks!