Move rubygems require into the actual test file.

Rakefile

@@ -1,6 +1,5 @@
 require 'rake'
 require 'rake/testtask'
-require 'rubygems'
 
 Rake::TestTask.new do |t|
   t.test_files = %w(test/twine_test.rb)

test/twine_test.rb

@@ -1,4 +1,5 @@
 require 'ERB'
+require 'rubygems'
 require 'test/unit'
 require 'twine'