Move to go.hacdias.com/indieauth

[hacdias]

I want to move to go.hacdias.com/indieauth, which is a breaking change. At the same time, I want to get rid of the major module versions. I really dislike the way Go handles it with the different import path, and I want to leverage the fact that this repository has few users and just make a PR to everyone.

• Rewrite history and remove major versions (breaking, never do this)
• Move to go.hacdias.com/indieauth
• Release 0.6.0 with breaking changes.
• Make PRs to users: https://github.com/hacdias/indieauth/network/dependents

Note: this is something I would never do, but since it's a small repo with few users, better break it now than later.