WordArray allows all characters except spaces

Fixes #1352.

WordArray would not register an offense for `['a@example.com', 'b@example.com']`, because it checked that each string should consist of word characters. So an email address containing `@` and `.` would not be a candidate for a `%w()`-style array.

As far as I can see, it should be enough to just check that the strings don’t contain spaces.
On the other hand it's not immediately clear what is the context in which this is interpolated (and it has to be interpolated on each method call).