fix "Mysql2::Error: This connection is in use by" in spec for Rails 4

Conflicts:
	Gemfile
	Gemfile.lock

Gemfile

@@ -86,6 +86,7 @@ group :test do
   # webkit and poltergeist don't seem to work yet
   gem 'selenium-webdriver'
   gem 'database_cleaner'
+  gem 'connection_pool'
   # need to include rspec components before i18n-spec or rake fails in test environment
   gem 'rspec-core'
   gem 'rspec-expectations'

Gemfile.lock

@@ -114,6 +114,7 @@ GEM
       execjs
     coffee-script-source (1.6.3)
     commonjs (0.2.7)
+    connection_pool (1.2.0)
     content_for_in_controllers (0.0.2)
     coveralls (0.7.0)
       multi_json (~> 1.3)
@@ -387,6 +388,7 @@ DEPENDENCIES
   client_side_validations
   client_side_validations-simple_form
   coffee-rails (~> 3.2.1)
+  connection_pool
   coveralls
   daemons
   database_cleaner

spec/support/shared_database.rb

@@ -5,7 +5,7 @@ class ActiveRecord::Base
     @@shared_connection = nil
        
     def self.connection
-      @@shared_connection || retrieve_connection
+      @@shared_connection || ConnectionPool::Wrapper.new(:size => 1) { retrieve_connection }
     end
 end
 # Forces all threads to share the same connection. This works on