Fix errors at rake docs and whitespace. (#183)

* Fix rake whitespace.
  Change the sed command format to run on GNU sed.
* Change hanna to rdoc to generate rdoc document.
  Because hanna latest version 0.1.12 is using very old rake as runtime dependency.
  That causes install error.
  rdoc does not have any runtime dependency. It looks better.

Rakefile

@@ -23,11 +23,11 @@ task :default => :spec
 desc "Generate RDoc"
 task :docs do
   FileUtils.rm_rf("doc")
-  require "rack/test"
-  system "hanna --title 'Rack::Test #{Rack::Test::VERSION} API Documentation'"
+  require "rack/test/version"
+  sh "rdoc --title 'Rack::Test #{Rack::Test::VERSION} API Documentation'"
 end
 
 desc 'Removes trailing whitespace'
 task :whitespace do
-  sh %{find . -name '*.rb' -exec sed -i '' 's/ *$//g' {} \\;}
+  sh %{find . -name '*.rb' -exec sed -i 's/ *$//g' {} \\;}
 end

rack-test.gemspec

@@ -25,6 +25,7 @@ request helpers feature.
   s.add_development_dependency 'rake', '~> 12.0'
   s.add_development_dependency 'rspec', '~> 3.6'
   s.add_development_dependency 'sinatra', '>= 1.0', '< 3'
+  s.add_development_dependency 'rdoc', '~> 5.1'
   # Keep version < 1 to supress deprecated warning temporary.
   s.add_development_dependency 'codeclimate-test-reporter', '~> 0.6'
   # For Thorfile. Run "bundle exec thor help" to see the help.