Better wording for README; add 'Development' section
Fix error in #rewrite_request_cookies:
it would errorneously rewrite request cookies that were set by the application
Reword and add comments, refactor some method names
Fix wrong RFC2822 formatting by Rack v1.1
Unify cookie selection of #delete_cookies_on_bad_path and #rewrite_request_cookies
Improve spec readability