paypro: move extensions to asn1.js
paypro: cleanup debugging code and comments.
paypro: lots of debugging. parse raw DER to get raw tbsCertificate.
paypro: more comments. debug.
paypro: move tbs parsing into common.
paypro: get chain validation working in the browser.
paypro: move validity and issuer validation into common.
paypro: remove old browser next pubKey code.
paypro: allow users to return verification properties via PayPro.verify.
paypro: immediately detect self signed certs and untrusted CAs.
paypro: add returnTrust to sign(). minor improvements.
paypro: fix uncatchable error in browser paypro.
test: add paypro test to verify a real PaymentRequest.