watch needs some fallback logic

[socketwiz]

Hey @mde I brought this up in IRC yesterday and thought I would dig into it a little more to see if there was something I could fix or file a bug report with node itself. The problem is here: https://github.com/mde/utilities/blob/master/lib/file.js#L199-L203

p is set to null on SmartOS. I read the documentation again and somehow overlooked this important paragraph:

Filename Argument

Providing filename argument in the callback is not supported on every platform (currently it's only supported on Linux and Windows). Even on supported platforms filename is not always guaranteed to be provided. Therefore, don't assume that filename argument is always provided in the callback, and have some fallback logic if it is null.

So is there anything that could be done here when p is null such that the restart mechanism in geddy would still work? I hacked it by just setting p = '.js' but I don't think thats the right approach for a proper fix.