Apply recommendation from thoughtbot/shoulda-matchers@a5623e7.

Gemfile

@@ -151,7 +151,7 @@ group :test do
   gem 'poltergeist'
   gem 'phantomjs', :require => 'phantomjs/poltergeist'
   # Set of rails validations matchers to describe models
-  gem 'shoulda'
+  gem 'shoulda-matchers', require: false
   # Extracted from RSpec 3 stub_model and mock_model
   gem 'rspec-activemodel-mocks'
   gem 'timecop'

Gemfile.lock

@@ -376,10 +376,6 @@ GEM
       sass (~> 3.2.2)
       sprockets (~> 2.8, < 2.12)
       sprockets-rails (~> 2.0)
-    shoulda (3.5.0)
-      shoulda-context (~> 1.0, >= 1.0.1)
-      shoulda-matchers (>= 1.4.1, < 3.0)
-    shoulda-context (1.2.1)
     shoulda-matchers (2.6.1)
       activesupport (>= 3.0.0)
     simplecov (0.8.2)
@@ -496,7 +492,7 @@ DEPENDENCIES
   rspec-rails
   rubocop
   sass-rails (>= 4.0.2)
-  shoulda
+  shoulda-matchers
   spring-commands-rspec
   sqlite3
   timecop

spec/spec_helper.rb

@@ -13,6 +13,7 @@ ENV['RAILS_ENV'] ||= 'test'
 require File.expand_path('../../config/environment', __FILE__)
 
 require 'rspec/rails'
+require 'shoulda/matchers'
 # To avoid confusion on missed migrations - use Rails 4 checker to ensure
 # all migrations applied
 ActiveRecord::Migration.maintain_test_schema!