Workaround node-static's Windows path resolution bug, add error handling, fixes #32

Looks like `node-static` has issues resolving relative paths in Windows. I've added error handling in this PR which clearly demonstrates the issue.

The current node-static stable release (0.7.3) does not resolve the relative path `./public` properly in Windows, hence the 403. ([screenshot](http://i.imgur.com/hYwNRFX.png))

Passing an absolute path avoids this issue.

p.s.: I've also tried updating to node-static's latest commit (https://github.com/cloudhead/node-static/commit/beb25d33ed7070142ca567896663e3ef7ba68787), however the relative paths are even more broken. It seems to duplicate the path, independent of using a relative or absolute path ([screenshot](http://i.imgur.com/H1t0yzY.png)). Hopefully this bug does not land on their next release, I'll try to analyse the issue on their repo and report it later.

Obligatory: Harmonic running on Windows from the native command prompt `;)`
![Harmonic running on Windows from the native command prompt](http://i.imgur.com/WwtsyAW.png)

fixes #32 (fo' real this time!)