applied original link to all content
Merge pull request #23 from hschoidr/master

automatically added original link to all header and titles
updated guides/rails_guides/markdown/renderer.rb
Merge pull request #24 from hschoidr/master

updated guides/rails_guides/markdown/renderer.rb
changed the link color of Chapters for original text.
Merge pull request #25 from hschoidr/master

changed the link color of Chapters for original text(main.css)
changed rails_guides_logo.gif to rails_guides_logo_ko.gif
Merge pull request #26 from hschoidr/master

changed rails_guides_logo.gif to rails_guides_logo_ko.gif
adjusted the width of rails_guides_logo_v.gif along the responsive design
Merge pull request #27 from hschoidr/master

adjusted the width of rails_guides_logo_ko.gif along the responsive design
translating guides/source/ko/active_support_core_extensions.md, updated
Merge pull request #28 from hschoidr/master

translating guides/source/ko/active_support_core_extensions.md, updated