Moved Mongo::VERSION to its own file

You shouldn't need to require mongo.rb just to generate the gemspec.

lib/mongo.rb

@@ -18,9 +18,7 @@
 
 $:.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
 
-module Mongo
-  VERSION = "1.3.1"
-end
+require 'mongo/version'
 
 module Mongo
   ASCENDING  =  1

lib/mongo/version.rb

@@ -0,0 +1,3 @@
+module Mongo
+  VERSION = "1.3.1"
+end

mongo.gemspec

@@ -1,4 +1,4 @@
-require "./lib/mongo"
+require File.expand_path('../lib/mongo/version', __FILE__)
 
 Gem::Specification.new do |s|
   s.name = 'mongo'