Remove development dependency on simplecov.

spec/spec_helper.rb

@@ -3,12 +3,6 @@ gem 'minitest'
 require 'minitest/spec'
 require 'minitest/autorun'
 require 'minitest/matchers'
-require 'simplecov'
-
-require 'process_shared'
-SimpleCov.start do
-  add_filter "/spec/"
-end
 
 class RangeMatcher
   def initialize(operator, limit)