Updated to work with node-canvas-v2

[TheDropOne]

No description provided.

[lukechilds]

Thanks.

The Base64 comparison errors can probably just be updated to use the new Base64 output. Canasv2 might just be using a new JPEG renderer that produces different binary data.

As long as it's doing what it should be doing (different quality setting etc) it's fine to just update them.

The Promise rejection looks like n API compatibility error though and will need to be fixed before merging.

errors › mergeImages rejects Promise if image load errors Promise returned by test never resolved

Btw, I think Canvasv2 includes a browser API shim, so it might be easier to just remove the Node.js specific code and use only the browser APIs. Then just setup the Canvasv2 browser shim if we're in Node.js. Not 100% sure that will work, haven't tested it, but it looks like it should.

Context: #65 (comment)