Fixed unicode decode bug in task overview.

Fixes https://github.com/4teamwork/opengever.phvs/issues/27

Bug happens only in single client setups. He appears if a task is displayed who has a special character in its title or its breadcrumb.

@lukasgraf 
You shouldn't put non-ASCII characters in source code as literals (`'ü'`). Use escape sequences instead (for example `u'\u00fcser1'` for unicode, or `'\xc3\xbcser1'` for UTF-8 bytestrings. Then you can also remove the `# -*- coding: utf-8 -*-` header. Otherwise all of this working correctly depends on your terminal and editor encoding, and on every person's that will edit this file in the future.