Pass an array to when.

The when parameter in a case statement expects a boolean condition or a
matching expression. I found this helpful;

http://ilikestuffblog.com/2008/04/15/how-to-write-case-switch-statements-in-ruby/

Based on that, I suspect I could also ditch the .to_s and just compare
class types.
add spec for config generate
Ah. After testing, and further reading I see that I need to splat these.

```
[variable =] case expression
when *array_1
  statements execute when the expression matches one
  of the elements of array_1
when *array_2
  statements execute when the expression matches one
  of the elements of array_2
end
```
no longer splat an array, or convert the class to a String.
Merge pull request #23 from miah/fix_config

Pass an array to when.