v0.8.0 — independence stated, the tour waits, and a row is not one thing

Added

• The trademark notice. PGSimCity is an independent, non-commercial
  educational visualization of PostgreSQL internals, not affiliated with,
  sponsored, endorsed or approved by Electronic Arts Inc., and SimCity is a
  trademark of Electronic Arts Inc. The notice appears on the loading screen,
  near the top of the README, in the help surface, and in a footer reachable
  from every screen including the observability page. The claim that this
  project contains no SimCity code, assets, artwork, logos, characters, audio or
  game content was added only after auditing for it — the favicon and boot mark
  are hand-authored SVG, the audio engine synthesises everything and ships no
  files, and the only traced artwork here is the PostgreSQL logo, a different
  trademark already disclaimed in NOTICE.
• Row versions. MVCC is what most reliably surprises someone arriving from
  another database, and it was modelled without being shown at the level where
  it teaches: dead tuples accumulated and vacuum removed them, but nothing said
  why. You can now see an UPDATE write a second copy of a row, two transactions
  looking at the same row and seeing different versions of it, and the old
  version becoming collectable only once the horizon passes it.

Changed

• The tour waits for you. Chapters advanced on a clock, whether or not you
  had finished reading — and at 60 to 110 words each, anyone who stopped to look
  at the thing being described lost their place. They now advance when you do,
  auto-play is opt-in, and the card says which chapter of fourteen you are on.