Fido2

** Add classes for implementing a server.
** Various small changes, some affecting backwards compatibility.

** Add conversion between string/int keys for AttestationObject.
** Replace internal Exceptions with built-in types.
** Bugfix: Don't use TimeoutError which isn't available on Python 2.

** Bugfix: Better handling of unplugged devices on MacOS and avoid leaking threads.

** Add server example.
** Parse AttestationObjects that use string keys (Webauthn).
** Fix bug in handling packets with the wrong channel id.

** Changed name of project to python-fido2 to better reflect its scope.
** Added attestation and assertion verification methods.
** A lot of name changes, moved classes, etc.
** New example for multi-device use.

** First beta release.