Update gemspec to remove "already initialized constant" warning [closes GH-264]

Gemfile

@@ -16,12 +16,4 @@ group :test do
   # For documentation
   gem "yard", "~> 0.6.1"
   gem "bluecloth"
-
-  platforms :mri_18 do
-    gem "ruby-debug"
-  end
-
-  platforms :mri_19 do
-    gem "ruby-debug19"
-  end
 end

vagrant.gemspec

@@ -1,4 +1,5 @@
-require File.expand_path("../lib/vagrant/version", __FILE__)
+$:.unshift File.expand_path("../lib", __FILE__)
+require "vagrant/version"
 
 Gem::Specification.new do |s|
   s.name          = "vagrant"