move target check outside of all format classes and operating on the final parsed JSON so that it works regardless of the input content type

more consistently returns HTTP 410 now

* mf2+html
* mf2+json
* feed+json
* xml
* instagram/facebook/github/xkcd

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

closes #16

* closes #14
* updated readme with details of the response
* includes `url` and `code` in the response with the final URL after following redirects and the HTTP status code returned

closes #18

If the input URL contains a fragment, finds the DOM tree at that ID and runs the subtree through the mf2 parser.

closes #15

errors fetching the URL should not result in a 400 response

closes #9

if a property such as `in-reply-to` is an h-cite, the URL is still returned as the `in-reply-to` value, and the h-cite object is available in a different part of the response.

closes #6