Escape HTML in the 404 page.

There is a reflected XSS in the development mode 404 page for clients
that don't URL-encode the request path. (I'm not aware of any major
browsers that do this, but you can see the idea with cURL.)
Added PROPFIND verb support
Update ShowExceptions to suit latest rack master

* Post 893a2c50 in rack/rack, the #pretty method used while generating
  the HTML error markup, implemented in Rack::ShowExceptions, returns a
  String instead of an Array. This change uses Array() to
  convert the exception string in both plain text and HTML modes
  to an array.
进行启动时候绑定参数的说明

-o 参数的说明以及绑定方式。
Merge pull request #908 from shenqihui/patch-1

进行启动时候绑定参数的说明
Added date to exception message
Fix to show local time instead of GMT
Prefer strings over symbols in Portuguese (PT and BR) and Spanish README
Prefer strings over symbols in German README
Merge pull request #910 from ausmarton/readme-symbols-to-strings

Prefer strings over symbols in Portuguese, Spanish and German README
Prefer strings over symbols in Japanese README
Merge pull request #909 from tayler1/master

Added date to exception message
Use default strftime in exception log added in #909
Merge pull request #911 from kami30k/readme-ja-symbols-to-strings

Prefer strings over symbols in Japanese README [ci skip]
Merge pull request #897 from markbates/master

Added PROPFIND verb support
Merge pull request #907 from kgrz/fix-error-with-rack-master

Update ShowExceptions to suit latest rack master
Revert "Added PROPFIND verb support"
Merge pull request #912 from sinatra/revert-897-master

Revert "Added PROPFIND verb support"
Fix docs when printing error from `env['sinatra.error']`.
Fixes #914
Merge pull request #915 from vipulnsward/fix-error-access

Fix docs when printing error from `env['sinatra.error']`.