checkin data is returned embedded like author data rather than in the `refs` object

closes #35

closes #40

thanks to the new backcompat in php-mf2 0.3.2

Refactors into a library that can be used separately from the API

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)

closes #20

skip image alt text for now

closes #34

replaced example post, closes #30

closes #36

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.