Don't run code coverage analyser to avoid additional dependency.

--- a/test/helper.rb.orig
+++ b/test/helper.rb
@@ -1,8 +1,3 @@
-require 'simplecov'
-SimpleCov.start do
-  add_filter '/test/'
-end
-
 require 'minitest/autorun'
 
 Dir[File.dirname(__FILE__) + '/fixtures/*.rb'].each do |f|