split out utility functions into test/app-utils.js.
more refactorings to test/app-utils.
even more refactorings to test/app-utils.
issuer.test.js now runs its own express server for hosting assertions.

this test now runs a LOT faster because it no longer needs to talk to
p2pu or github to find images and stuff.
generate hosted assertions for tests completely dynamically, enforcing DRY.