Finish deprecation of all U2F-specific classes

[Firehed]

The additions to the changelog best summarize this, but as all of the legacy u2f.js format support will be dropped in the next major release, all of the classes and related functionality surrounding them is being deprecated.

There's a pretty substantial amount of test updates that go along with this to decouple the server tests from the U2F-specific data formats, but #13 paved the way for that to happen.

[codecov[bot]]

Codecov Report

Merging #36 (b9b8db5) into master (bbe2e40) will not change coverage. The diff coverage is n/a.

@@             Coverage Diff             @@
##              master       #36   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       140       140           
===========================================
  Files             22        22           
  Lines            559       559           
===========================================
  Hits             559       559           

Impacted Files	Coverage Δ
src/AppIdTrait.php	100.00% <ø> (ø)
src/ChallengeTrait.php	100.00% <ø> (ø)
src/ClientData.php	100.00% <ø> (ø)
src/KeyHandleTrait.php	100.00% <ø> (ø)
src/RegisterRequest.php	100.00% <ø> (ø)
src/RegisterResponse.php	100.00% <ø> (ø)
src/ResponseTrait.php	100.00% <ø> (ø)
src/Server.php	100.00% <ø> (ø)
src/SignRequest.php	100.00% <ø> (ø)
src/SignResponse.php	100.00% <ø> (ø)
... and 2 more

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