use parseHTMLValue function for event description

Add $base to default config

allows the XKCD XML feeds to be parsed with the feed parser

using fork of picofeed with 0.1.38 tag on aaronpk repo

the zend security model runs libxml_disable_entity_loader to disable it so it's fine to allow

* adds test of instagram-atom feed with individual authors per item
* dedupes atom/rss title if it's a prefix of the content

if an item has multiple URL values, return the one that is on the same domain

# Conflicts:
#	README.md
#	composer.json
#	composer.lock

includes info on feed parsing

Treats `https://example.com` and `https://example.com/` as equivalent when comparing URLs. Closes #33

closes #32

uses the video's poster frame as the photo if any of the multi-post images are videos

according to http://microformats.org/wiki/h-entry the rsvp values should be interpreted case-insensitive

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