use cgi/util.rb or cgi.rb instead of dead copy

reduce warning: regexp match /.../n against to UTF-8 string
add String#b (ruby 2.0 feature)
use String#b in pages (fix test failures)
String#b returns a copied string
avoid ruby 1.9.3's CGI.escape encoding bug, fixed in 2.0.0
merge expected
Merge pull request #32 from znz/use-cgi-util

use cgi/util.rb or cgi.rb instead of dead copy