/404 returns 302, /500 returns 200
added problems page
removed node.js dependencies
added /problems endpoint
render markdown problems
use haml template with markdown
deleted useless files
added problem 1 and 2
Merge branch 'problems' into break-404-500

Conflicts:
	config.ru
added markdown style sheets
added highlight.js
hide hints
updated css
deleted useless files
fixed small bugs
small fix
deleted script
Merge pull request #55 from junsumida/break-404-500

/404 returns 302, /500 returns 200 + 問題ページ