Updated crossorigin settings

The crossorigin settings are currently breaking image tests in Firefox and Safari when the images are not cross-domain (e.g. images specified as base64 strings, or using relative pathing).

This change enables CORS on the image if and only if the image is 1) specified using absolute pathing with the HTTP or HTTPS protocol and 2) the image is from a different domain than resemble.js is being run on.
Call hiddenImage.onload if image is cached.
Added two distance-based types of errorPixelTransform
Renamed difference intensity properties
Merge branch 'kamilbielawski-distance_based_intensity'
Merge branch 'master' of https://github.com/johnpduane/Resemble.js into johnpduane-master
Merge branch 'johnpduane-master'
Merge branch 'master' of https://github.com/Shadowblazen/Resemble.js into Shadowblazen-master
Merge branch 'Shadowblazen-master'
Bump minor