if the document contains a link to the target, but that link is not in the parsed result, don't return an error, but also don't return the parsed document

closes #150

XRay now looks for images inside the HTML and does not consider those empty posts

To make it possible to consume feeds of pre-rendered Microformats2 JSON
data, we need to be able to discover that it is a Microformats2 JSON
file using the known MIME types documented  in
http://microformats.org/wiki/microformats2-mime-type

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

for https://github.com/aaronpk/Aperture/issues/56

closes #89

closes #92

closes #86

more consistently returns HTTP 410 now

This adds a new property, "meta", which includes alt text and has room to include additional properties later.

closes #85

replaces #78

closes #79

* a single h-entry and h-card, where the h-entry has no URL, will result in a permalink page with that h-entry
* multiple h-entrys followed by an h-card is a feed

closes #77

including from rel=alternate

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

returns a new property `post-type` next to `type`

closes #25

closes #73

parse from both link tags and the u-redirect-uri property

adds script to refresh the downloaded instagram data for the tests as well

instagram seems to have rolled out the `graphql` key everywhere now