v8.0.0

Never released to crates.io

• Breaking change: #177 the order of -x and -s is now respected. (This never actually happened. The code was not merged.)

  Example: cargo watch -s 'echo before' -x test -s 'echo after'
  Before: would run cargo test && echo before && echo after.
  Now: runs echo before && cargo test && echo after.

• Experimental: --notify/-N flag sends a desktop notification when a change is observed (which may or may not trigger a command restart). While objectively the better behaviour would be to notify on command finish and vary the notification on exit status, we just can't do that at the moment with the current architecture.