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

Conflicts:
	Gemfile
	Gemfile.lock

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