python-chess v0.28.0

Changes:

* Dropped support for Python 3.4 (end of life reached).
* `chess.polyglot.Entry.move` **is now a property instead of a method**.
  The raw move is now always decoded in the context of the position (relevant
  for castling moves).
* `Piece`, `Move`, `BaseBoard` and `Board` comparisons no longer support
  ducktyping.
* FENs sent to engines now always include potential en-passant squares, even if
  no legal en-passant capture exists.
* Circular SVG arrows now have a `circle` CSS class.
* Superfluous dashes (-) in EPDs are no longer treated as opcodes.
* Removed `GameCreator`, `HeaderCreator` and `BoardCreator` aliases for
  `{Game,Headers,Board}Builder`.

Bugfixes:

* Notation like `Kh1` is no longer accepted for castling moves.
* Remove stale files from wheels published on PyPI.
* Parsing Three-Check EPDs with moves was always failing.
* Some methods in `chess.variant` were returning bool-ish integers, when they
  should have returned `bool`.
* `chess.engine`: Fix line decoding when Windows line-endings arrive seperately
  in stdout buffer.
* `chess.engine`: Survive timeout in analysis.
* `chess.engine`: Survive unexpected `bestmove` sent by misbehaving UCI engines.

New features:

* **Experimental type signatures for almost all public APIs** (`typing`).
  Some modules do not yet internally pass typechecking.
* Added `Board.color_at(square)`.
* Added `chess.engine.AnalysisResult.get()` and `empty()`.
* `chess.engine`: The `UCI_AnalyseMode` option is still automatically managed,
  but can now be overwritten.
* `chess.engine.EngineProtocol` and constructors now optionally take
  an explicit `loop` argument.