Release 0.5.1

What's Changed

• Fix P0 NPE in ServerConnectionCache causing test failures by @Hellblazer in #97
• Simplify release workflow by @Hellblazer in #96
• Fix GossipPropagationTest convergence by using calculated rebuttal timeout by @Hellblazer in #98

Full Changelog: v0.5.0...v0.5.1