Games 0.3.0

The first release. Fourteen games that had only ever run from a build
directory on one machine now download as a single file on Linux or Windows,
and eight of them remember where you left off.

Added

• Games downloads as one file, for Linux and for Windows (GHUB-0025)
  No compiler, no build steps, nothing to install: grab the AppImage on
  Linux or the zip on Windows and run it. Both carry their own copy of Qt,
  so they work on a machine that has never had it, and both ship the
  licence texts that bundling Qt requires. Every push is now built and
  tested on both operating systems too, so a change that breaks Windows is
  caught by the machine rather than by whoever downloads it next.

• Minesweeper, Reversi, Draughts and 2048 remember where you left off (GHUB-0010)
  Close one of them mid-game and it is exactly as you left it next time you
  open it — no save dialog, nothing to press. Minesweeper keeps your clock
  and stays paused if you paused it; Draughts still shows where the computer
  last moved. A finished game leaves nothing behind, so you never resume onto
  your own final score.

• Klondike, Spider, FreeCell and Pyramid save and resume (GHUB-0008)
  Close a game of patience part way through and it is waiting where you
  left it next time you open it. A shared card codec does all four, and
  checks the cards coming back really are the pack that was dealt before
  it puts them on the table.

• Chess remembers a game in progress — the board, whose move it is, the moves
  behind it and the strength all come back when you reopen it (GHUB-0006).