Handle null as JSON POST parameter on /discover.
Bugfix — If a parameter is set to null, consider it as missing.
Release 0.4.4
Bug — Duration is defined as being in seconds.
Release 0.4.5
Upgrade dependency from jwcrypto to browserid-crypto.
Merge pull request #134 from mozilla-services/issue133/use-browserid-crypto

Bug 1096102 — Upgrade dependency from jwcrypto to browserid-crypto.
Sync master and 0.4.x
Update changelog
Bug 1088105 — Add the lastVerifiedAt parameter to the certificate.