auth module and utf8 chars

In its current state the auth module does not accept names containing utf8 chars.
Commands containing german umlauts or other utf8 chars (e.g. `hubot Jöhn dööö has role test`) are ignored.

One way to fix this is to accept any char as input instead of the limited range using `.+`.

Another way would be to use the [XRegExp Unicode Addon](http://xregexp.com/plugins/), but that would create a dependency.

The PR contains the first solution