Remove assumption that all absolute paths start with '/'

I was unable to serve static files using hapi on Windows. The reason for the failure is that there are a number of places in the framework where it is assumed that a static path must begin with `'/'`.

I've extracted the `Path.isAbsolute()` function from node core that is available in the `0.11.x` series as a stand-alone module. I've also extracted the tests relating to this new function in the newly created `absolute-path` module.

The code was taken from: joyent/node@90266750617adb1ce1ca4ce43fe48f9b0fa11343

The `absolute-path` module can be found at [node-absolute-path](/filearts/node-absolute-path)

Please note: As I am on Windows, I do not get meaningful results from `make test`.