Authl v0.3.3

Just a tiny fix in this; it works around an inconsistency between the IndieAuth spec and IndieAuth.com’s implementation. Normally I’d just be all, “this is a bug in IndieAuth.com” but that’s the most popular IndieAuth endpoint right now so I decided it was prudent to make a compromise. And really it’s a good idea to always specify an Accept: header anyway.

Thanks to Colin for bringing this to my attention.