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

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.

this allows you to use XRay without creating a config file using its default settings (currently only caching disabled)

closes #18

if the photo has a location, the timezone is set on the published date

use fork of php-mf2 until https://github.com/indieweb/php-mf2/pull/83 is merged

allow only a basic set of tags, and remove any non-mf2 classes

closes #2

sanitize the HTML returned in the content property. allows a common set of HTML tags.

for #2