bundle install failing with `install_in_parallel': undefined method `[]'

Gemfile

source 'https://rubygems.org'

group :development do
  gem 'spring'
  gem 'rb-readline'
  gem 'rack-mini-profiler'
  gem 'better_errors'
  gem 'binding_of_caller'
  gem 'flamegraph'
  gem 'meta_request'
  gem 'guard-rspec', '~> 4.2.8'
end

group :development, :test do
  gem 'minitest'
  gem 'pry',                  '~> 0.9.12.6'
  gem 'pry-doc'
  gem 'pry-rails'
  gem 'awesome_print',        '~> 1.2.0'
  gem 'rspec-rails',          '~> 3.0.0.beta2'
  gem "shoulda-matchers"
  gem 'factory_girl_rails',   '~> 4.3.0'
  gem 'database_cleaner',     '~> 1.2.0'
  gem 'capybara',             :git => "git://github.com/jnicklas/capybara.git"
  gem 'capybara-webkit'
  gem 'phantomjs',            '1.9.7.1'
  gem 'foreman',              '~> 0.63.0'
  gem 'jasmine-rails'
  gem 'debugger'
  gem 'autotest-rails',       '~> 4.1.0'
  gem 'launchy'
end

group :production do
  gem 'rails_12factor'
end

gem 'rails',              '~> 4.1.0'
gem 'pg',                 '~> 0.17.1'

gem 'haml-rails',         '~> 0.5.3'
gem 'sass-rails',         '~> 4.0.0'
gem 'compass-rails',      '~> 1.1.2'
gem 'bootstrap-sass',     '~> 3.0.3'
gem 'uglifier',           '>= 1.3.0'
gem 'coffee-rails',       '~> 4.0.0'
gem 'jquery-rails',       '~> 3.1.0'
gem 'jquery-turbolinks',  '~> 2.0.2'
gem 'jquery-datatables-rails', '~> 1.12.2'
gem 'turbolinks'
gem 'jbuilder',           '~> 1.2'
gem 'unicorn',            '~> 4.8.2'
gem 'font-awesome-rails'
gem 'chosen-rails',       '~> 1.1.0'
gem "selectize-rails"
gem 'public_activity',    '~> 1.4.1'
gem 'twilio-ruby',        '~> 3.11.5'
gem 'ancestry',           '~> 2.0.0'
gem 'remotipart',         '~> 1.0.5'
gem 'paperclip',          :git => "git://github.com/thoughtbot/paperclip.git"
gem 'fog'
gem 'unf'
gem 'sucker_punch',       '~> 1.0'
gem 'newrelic_rpm'
gem 'wicked_pdf',         '~> 0.10.2'
gem 'wkhtmltopdf-binary', '~> 0.9.9.1'

group :doc do
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
gem 'bcrypt-ruby',        '~> 3.1.2'

ruby "2.1.1"