Fix gemspec

Author: Carlos Silva

torque_postgresql.gemspec

@@ -2,6 +2,7 @@ $:.push File.expand_path('../lib', __FILE__)
 
 # Maintain your gem's version:
 require 'torque/postgresql/version'
+require 'date'
 
 # Describe your gem and declare its dependencies:
 Gem::Specification.new do |s|