0.0.1.dev22

vbump for release, drop 3.6 support, bump orthauth dep

can't test on 3.6 easily anymore

Ror add mapping Funder type, likely needs review

better handling of head failures, try to get if > 400 because many
remotes have incorrect implementations of head

a note here also that requests response objects have a .history attr
which holds the whole resolution chain (duh)

better error messages and more notes about issues with naming of
ResolutionError, likely prefer MessageReceivedButError