PNG baking broken in openbadges-bakery, works in openbadges-bakery-v2 (I think), both fail if writing assertion to SVG

Two main problems:

1. Can't write to PNG in openbadges-bakery package, but does work in -v2
2. The file `./lib/svg.js` appears to be looking for openbadge 1.0-style assertion objects with a `.verify` and `.verify.url` properties that don't exist in version 2.0, but the `png.js` file appears to look for the correct assertion object format.