Fix a problem to redirect wikipage named by multi-byte characters

In some specific case, redirect path (created from route params) is incorrect.

(from src/main/scala/app/SignInController.scala)
````
 46     session.getAndRemove[String](Keys.Session.Redirect).map { redirectUrl =>
````
`redirectUrl` is expected to be encoded,
but scalatra decodes route params by rl.UrlCodingUtils via ScalatraBase.UriDecoder.

In this result, we can't redirect wikipage named by multi-byte characters.

Demo:
* from http://cdn-ak.f.st-hatena.com/images/fotolife/s/smly/20131019/20131019134651.png
* to http://cdn-ak.f.st-hatena.com/images/fotolife/s/smly/20131019/20131019134652.png

To avoid this problem, I add dirty workaround to encode redirect path.