moves XRay classes to `p3k\XRay` namespace
* removes the HTTP classes from this project and uses p3k-http library instead
* reorganizes the XRay classes into a psr-4 compatible folder
* moves controller autoload into -dev in preparation for turning this into a library (#17)
Grabs rel values from both HTTP headers and link tags and merges them together, and resolves any relative values. Also returns the final URL requested and the HTTP response.