Merge branch 'master', remote branch 'upstream/master'
First convert.
Change extension.
Removed bit of unneeded RDoc stuff at bottom.
Convert european portuguese README to Markdown
Remove obsolete portuguese RDoc README
Merge pull request #657 from gcapizzi/portuguese_readme_md

Convert european portuguese README to Markdown
Merge pull request #656 from yb66/convert-jp-rdoc-to-md

Convert jp rdoc to md
Use `headers` instead of `header`, since in `Rack::Response` `headers` is an alias for `header` and `headers` is widely used in Sinatra. It's confusing that in `Sinatra::Response#finish` both `headers` and `header`.
Merge pull request #659 from patriciomacadden/header-headers

Use `headers` method instead of `header` method in `Sinatra::Response`