Bugfix directory of Japanese name

directory list

```sh
 $ ls -l
drwxrwxrwx 2 naoto naoto      4096  7月 18 23:07 Fate_Kaleid_Liner_プリズマ☆イリヤ
```

playing to shuffle

```sh
 $ airplayer play ./ -s
/home/naoto/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/uri/common.rb:176:in `split': bad URI(is not URI?): Fate_Kaleid_Liner_プリズマ☆イリヤ (URI::InvalidURIError)
        from /home/naoto/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/uri/common.rb:211:in `parse'
        from /home/naoto/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/uri/common.rb:747:in `parse'
        from /home/naoto/dev/airplayer/lib/airplayer/media.rb:51:in `playable?'
        from /home/naoto/dev/airplayer/lib/airplayer/playlist.rb:46:in `block in media_in_local'
        from /home/naoto/dev/airplayer/lib/airplayer/playlist.rb:45:in `map'
        from /home/naoto/dev/airplayer/lib/airplayer/playlist.rb:45:in `media_in_local'
        from /home/naoto/dev/airplayer/lib/airplayer/playlist.rb:16:in `add'
        from /home/naoto/dev/airplayer/lib/airplayer/app.rb:11:in `play'
        from /home/naoto/dev/airplayer/vendor/bundle/ruby/2.0.0/gems/thor-0.18.1/lib/thor/command.rb:27:in `run'
        from /home/naoto/dev/airplayer/vendor/bundle/ruby/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:120:in `invoke_command'
        from /home/naoto/dev/airplayer/vendor/bundle/ruby/2.0.0/gems/thor-0.18.1/lib/thor.rb:363:in `dispatch'
        from /home/naoto/dev/airplayer/vendor/bundle/ruby/2.0.0/gems/thor-0.18.1/lib/thor/base.rb:439:in `start'
        from bin/airplayer:5:in `<main>'
```