message: Clarify `README`
diff: @@ -156,11 +156,10 @@ its own standalone crate, as it could potentially benefit other engines and
  applications. I thought it was a great idea, and after a bit of work... Iced is
  here!
  -As an interesting note, Iced does not rely on reference counting and interior
  -mutability. There is not a single `Rc`, `RefCell`, or similar used
  -directly in the library. As a consequence, compiler guarantees stay intact and
  -many kinds of pesky bugs and runtime errors are banished. No spooky action at
  -a distance!
  +As an interesting note, the core of Iced does not rely on interior mutability.
  +Usage of types like `RefCell` is restricted to runtime boundaries. As a
  +consequence, compiler guarantees stay intact and many kinds of pesky bugs and
  +runtime errors are banished. No spooky action at a distance!
  [this pull request]: https://github.com/hecrj/coffee/pull/35
  [`stretch`]: https://github.com/vislyhq/stretch
  