[phobos] Make Tuple.toString useful

[Q. Schroll via phobos]

>> I'm new to this, ....

> The best way to do something like this is to create a pull 
> request. This will not only give you credit for the change and 
> make the code easy to add to Phobos, but it will make sure it 
> doesn’t break any existing tests.
>
> Please have a look here: http://wiki.dlang.org/Pull_Requests 
> <http://wiki.dlang.org/Pull_Requests>
>
> -Steve

Thanks. This is the information I didn't find. Thank you very 
much.