Revert "The rails gem doesn't have a lib directory."

RubyGems requires at least one require_path.

This reverts commit 3001728325.

rails.gemspec

@@ -15,9 +15,8 @@ Gem::Specification.new do |s|
   s.homepage          = 'http://www.rubyonrails.org'
   s.rubyforge_project = 'rails'
 
-  s.bindir            = 'bin'
-  s.executables       = ['rails']
-  s.require_paths     = []
+  s.bindir             = 'bin'
+  s.executables        = ['rails']
 
   s.add_dependency('activesupport',  version)
   s.add_dependency('actionpack',     version)