Fix errors at rake docs and whitespace.

[junaruga]

This fixes #182

Summary

• Fix rake whitespace.
  I changed the sed command format to run on GNU sed. Another version sed has been used before?
• 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.

Ref:

• https://rubygems.org/gems/hanna
  runtime dependencies
  rake ~> 0.8.2
• https://rubygems.org/gems/rake
  rake is 12.0.0

Use cases

whitespace

$ vi lib/rack/test.rb

$ git status
On branch hotfix/fix-rake-docs-and-whitespace
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   lib/rack/test.rb
...

$ git diff
diff --git a/lib/rack/test.rb b/lib/rack/test.rb
index b7288c6..8aa3f85 100644
--- a/lib/rack/test.rb
+++ b/lib/rack/test.rb
@@ -6,7 +6,7 @@ require "rack/test/mock_digest_request"
 require "rack/test/utils"
 require "rack/test/methods"
 require "rack/test/uploaded_file"
-require "rack/test/version"
+require "rack/test/version"   <= tailing space
 
 module Rack
   module Test

$ bundle exec rake whitespace
find . -name '*.rb' -exec sed -i 's/ *$//g' {} \;

$ git status
<= no difference

docs

$ bundle exec rake docs
...
rdoc --title 'Rack::Test 0.6.3 API Documentation'
Parsing sources...
...

Then see doc/index.html.

[dennissivia]

LGTM

[junaruga]

Thanks for the reviewing!