Stitcher beta 2

The second beta release of Stitcher ties a lot of loose ends together, getting ready for real production sites.

# Installation

composer require pageon/stitcher-core @beta

# Changelog

Note the a few config parameters are changed. These changes might fall under the category "breaking", but were really needed in order to get a more consistent API, before a real 1.0.0 release comes along.