update introductory section in README.jp.md

Update Route and Return values sections in README.jp.md

Add Custom Route Matchers section in README.jp.md

Update Views / Templates section in README.jp.md

Update Filters and Helpers sections in README.jp.md

Correct some wordings

Add Using Sessions section in README.jp.md

Update Halting and Passing sections in README.jp.md

Add original english titles to each section in README.jp.md

Add missing sections in original language

Add TOC and modify section titles in README.jp.md

Fix broken links in toc

Update Mime Types, Accessing the Request Object and Configuration sections in README.jp.md

Update Error Handling, Rack Middleware, and Testing, Sinatra::Base sections in README.jp.md

Update Scopes and Binding section in README.jp.md

Update Requirement, The Bleeding Edge, Versioning, and Further Reading sections in README.jp.md

Remove some original text from section titles

Update Triggering Another Route, Setting Body, Status..., Streaming Responses, and Logging sections in README.jp.md

Update Generating URLs, Browser Redirect, Cache Control, Sending Files, Attachments, Dealing with Date and Time, and Looking Up Tempalte Files in README.jp.md

Update Configuration and Environments sections in README.jp.md

Remove some original texts

Fix and Modify irrelevant lines in README.jp.md
Merge pull request #832 from melborne/update-readme-jp

Update README.jp.md as a whole